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Transfusion-transmitted hepatitis B virus infection

Open AccessPublished:June 10, 2009DOI:https://doi.org/10.1016/j.jhep.2009.05.020
      Hepatitis B virus (HBV) remains a major risk of transfusion-transmitted infection due to the pre-seroconversion window period (WP), infection with immunovariant viruses, and with occult carriage of HBV infection (OBI). Reduction of HBV residual risk depends upon developing more sensitive HBV surface antigen (HBsAg) tests, adopting anti-HBc screening when appropriate, and implementing HBV nucleic acid testing (NAT), either in minipools or more efficiently in individual samples. HBV NAT combines the ability to significantly reduce the window period and to detect occult HBV carriage substantiating decades of clinical observation that HBsAg-negative/anti-HBc-positive blood could transmit HBV. Clinical observations suggest limited transmission rate of occult HBV compared to WP. Low transmission rate might be related to low viral load observed in OBIs or to the presence of mutants associated with occult carriage. OBIs carrying detectable anti-HBs (∼50%) are essentially not infectious by transfusion. However, recent data suggest that the neutralizing capacity of low anti-HBs may be inefficient when overcome by exposure to high viral load. Anti-HBc blood units without detectable anti-HBs appear moderately infectious except in immunocompromised recipients. Immunodeficient elderly and patients receiving immunosuppressive treatments may be susceptible to infection with lower infectious dose even in the presence of anti-HBs. The immune status of blood recipients should be taken into consideration when investigating “post-transfusion” HBV infection. Pre-transfusion testing and post-transfusion long-term follow-up of recipients, and molecular analysis of the virus infecting both donor and recipient are critical to definitively incriminate transfusion in the transmission of HBV.

      Keywords

      Abbreviations:

      HBV (hepatitis B virus), WP (window period), OBI (occult HBV infection), HBsAg (HBV surface antigen), NAT (nucleic acid testing), EIA (enzyme immunoassay), ELISA (enzyme-linked immunosorbent assay), CLIA (chemiluminescence immunoassay), CLEIA (chemiluminescent enzyme immunoassay), FFP (fresh-frozen plasmas), RBC (red blood cells), PC (platelet concentrates)

      1. Introduction

      Hepatitis B virus (HBV) remains a major public health problem worldwide. In highly endemic areas (⩾8% HBsAg prevalence) including Sub-Saharan Africa, South East Asia, China and the Amazon Basin, transmission occurs essentially vertically or horizontally at young ages, and 70–90% of the adult population has serologic evidence of prior infection (anti-HBc). Countries from the Mediterranean area, Eastern Europe and the Middle East with intermediate endemicity (2–7% HBsAg) have a mix of vertical, horizontal, health-care-related (i.e. blood transfusion), unsafe injections, and sexual routes of transmission. In areas of low endemicity (<2% HBsAg) including Western and Northern Europe, North America, part of South America, and Australia, transmission occurs mainly among young adults through sexual contacts or unsafe injections [
      • Shepard C.W.
      • Simard E.P.
      • Finelli L.
      • Fiore A.E.
      • Bell B.P.
      Hepatitis B virus infection: epidemiology and vaccination.
      ].
      Before 1970, approximately 6% of multi-transfused recipients acquired transfusion-transmitted HBV. Over the last four decades, the risk of transfusion-transmitted hepatitis B virus has been steadily reduced, yet HBV transmission remains the most frequent transfusion-transmitted viral infection. The residual risk of HBV transfusion transmission is mainly related to blood donations negative for HBsAg that have been collected either during the pre-seroconversion ‘window period’ (WP) defined as the time between infection and detection of a viral antigen or antibody marker, or during the late stages of infection. Implementation of HBV DNA screening has the potential to significantly reduce the WP and to reveal ‘occult’ HBV infection or carriage (OBI) [
      • Allain J.P.
      Occult hepatitis B virus infection: implications in transfusion.
      ]. OBI is defined as the presence of HBV DNA without detectable HBsAg outside the WP. It is generally admitted that pre-seroconversion WP infections are most likely to transmit HBV but transmission from occult HBV infection remains debated [
      • Hollinger F.B.
      Hepatitis B virus infection and transfusion medicine: science and the occult.
      ].
      The aim of the present review is to examine the residual risk of transfusion-associated HBV transmission according to HBV screening strategies of blood donations, and the infectivity of HBV-containing blood products according to the immune status of recipients.

      2. Detection of HBV in blood donors

      2.1 Improvements and limitations of HBsAg testing

      HBsAg tests remain the first-line of blood screening for HBV. Current HBsAg screening assays are enzyme immunoassays (EIAs), including enzyme-linked immunosorbent assays (ELISAs), and chemiluminescence immunoassays (CLIAs). These different assays have sensitivity ranging between <0.1 and 0.62 ng of HBsAg per mL (1 ng/ml corresponds to approximately 2 IU/mL) [
      • Biswas R.
      • Tabor E.
      • Hsia C.C.
      • Wright D.J.
      • Laycock M.E.
      • Fiebig E.W.
      • et al.
      Comparative sensitivity of HBV NATs and HBsAg assays for detection of acute HBV infection.
      ,
      • Scheiblauer H.
      • Soboll H.
      • Nick S.
      Evaluation of 17 CE-marked HBsAg assays with respect to clinical sensitivity, analytical sensitivity, and hepatitis B virus mutant detection.
      ]. A chemiluminescent enzyme immunoassay (CLEIA) prototype has been developed that claims a sensitivity of 0.22 mIU/mL and the ability to reduce the WP by ∼17 days compared to the CLIA systems in use [
      • Matsubara N.
      • Kusano O.
      • Sugamata Y.
      • Itoh T.
      • Mizuii M.
      • Tanaka J.
      • et al.
      A novel hepatitis B virus surface antigen immunoassay as sensitive as hepatitis B virus nucleic acid testing in detecting early infection.
      ].
      Due to high cost and considerable equipment requirements, these HBsAg assays may not be affordable for small-scale blood services particularly in resource-limited developing countries. Rapid immunochromatographic HBsAg tests have been developed and were evaluated in high prevalence areas [
      • Lien T.X.
      • Tien N.T.
      • Chanpong G.F.
      • Cuc C.T.
      • Yen V.T.
      • Soderquist R.
      • et al.
      Evaluation of rapid diagnostic tests for the detection of human immunodeficiency virus types 1 and 2, hepatitis B surface antigen, and syphilis in Ho Chi Minh City, Vietnam.
      ,
      • Owusu-Ofori S.
      • Temple J.
      • Sarkodie F.
      • Anokwa M.
      • Candotti D.
      • Allain J.P.
      Predonation screening of blood donors with rapid tests: implementation and efficacy of a novel approach to blood safety in resource-poor settings.
      ,
      • Randrianirina F.
      • Carod J.F.
      • Ratsima E.
      • Chrétien J.B.
      • Richard V.
      • Talarmin A.
      Evaluation of the performance of four rapid tests for detection of hepatitis B surface antigen in Antananarivo, Madagascar.
      ]. Comparative studies showed that rapid tests are less sensitive than most EIAs [
      • Lien T.X.
      • Tien N.T.
      • Chanpong G.F.
      • Cuc C.T.
      • Yen V.T.
      • Soderquist R.
      • et al.
      Evaluation of rapid diagnostic tests for the detection of human immunodeficiency virus types 1 and 2, hepatitis B surface antigen, and syphilis in Ho Chi Minh City, Vietnam.
      ,
      • Owusu-Ofori S.
      • Temple J.
      • Sarkodie F.
      • Anokwa M.
      • Candotti D.
      • Allain J.P.
      Predonation screening of blood donors with rapid tests: implementation and efficacy of a novel approach to blood safety in resource-poor settings.
      ,
      • Allain J.P.
      • Candotti D.
      • Soldan K.
      • Sarkodie F.
      • Phelps B.
      • Giachetti C.
      • et al.
      The risk of hepatitis B virus infection by transfusion in Kumasi, Ghana.
      ].
      Differences in analytical sensitivity and specificity in detection of HBsAg from viruses of different genotypes have been reported among commonly used EIAs [
      • Weber B.
      • Dengler T.
      • Berger A.
      • Doerr H.W.
      • Rabenau H.
      Evaluation of two new automated assays for hepatitis B virus surface antigen (HBsAg) detection: IMMULITE HBsAg and IMMULITE 2000 HBsAg.
      ,
      • Olinger C.M.
      • Weber B.
      • Otegbayo J.A.
      • Ammerlaan W.
      • van der Taelem-Brulé N.
      • Muller C.P.
      Hepatitis B virus genotype E surface antigen detection with different immunoassays and diagnostic impact of mutations in the preS/S gene.
      ]. Mutations associated with conformational and hydrophobic changes within and outside the immunogenic major hydrophilic region (MHR) of the S antigen (the main target for capture antibodies used in diagnostic tests) and with reduced synthesis or secretion of HBsAg may account solely or in conjunction for the failure or a significant decrease in detecting HBsAg by immunoassays [
      • Weber B.
      Genetic variability of the S gene of hepatitis B virus: clinical and diagnostic impact.
      ]. Mutations may occur naturally from escaping active or passive immunity or antiviral therapy. Occurrence of such mutant strains may reach ∼30% in areas of high endemicity following vaccination programs [
      • Hsu H.-Y.
      • Chang M.-H.
      • Ni Y.-H.
      • Chen H.-L.
      Survey of hepatitis B surface variant infection in children 15 years after a nationwide vaccination programme in Taiwan.
      ,
      • Theamboonlers A.
      • Chongsrisawat V.
      • Jantaradsamee P.
      • Poovorawan Y.
      Variants within the “a” determinant of HBs gene in children and adolescents with and without hepatitis B vaccination as part of Thailand’s Expanded Program on Immunization (EPI).
      ]. Another cause of failure in detecting HBsAg may be the concomitant presence of hepatitis B surface antibodies (anti-HBs) leading to the formation of circulating immune complexes not or poorly displaced by HBsAg capture antibodies [
      • Joller-Jemelka H.I.
      • Wicki A.N.
      • Grob P.J.
      Detection of HBs antigen in “anti-HBc alone” positive sera.
      ,
      • Zhang J.M.
      • Xu Y.
      • Wang X.Y.
      • Yin Y.K.
      • Wu X.H.
      • Weng X.H.
      • et al.
      Coexistence of hepatitis B surface antigen (HBsAg) and heterologous subtype-specific antibodies to HBsAg among patients with chronic hepatitis B virus infection.
      ].
      HBsAg-positive/HBV DNA-negative samples are found in 2–16% of blood donor carriers [
      • Allain J.P.
      • Candotti D.
      • Soldan K.
      • Sarkodie F.
      • Phelps B.
      • Giachetti C.
      • et al.
      The risk of hepatitis B virus infection by transfusion in Kumasi, Ghana.
      ,
      • Kiely P.
      • Stewart Y.
      • Castro L.
      Analysis of voluntary blood donors with biologic false reactivity on chemiluminescent immunoassays and implications for donor management.
      ,

      Vermeulen M, Lelie N, Sykes W, Crookes R, Swanevelder J, Gaggia L, et al. Impact of individual-donation nucleic acid testing on risk of human immunodeficiency virus, hepatitis B virus, and hepatitis C virus transmission by blood transfusion in South Africa. Transfusion 2009 Feb 27. [Epub ahead of print].

      ]. Documented cases of donors confirmed HBsAg-positive a few days after HBV vaccination were reported as a cause of unnecessary deferral of blood donors [
      • Dow B.C.
      • Yates P.
      • Galea G.
      • Munro H.
      • Buchanan I.
      • Ferguson K.
      Hepatitis B vaccines may be mistaken for confirmed hepatitis B surface antigen-positive blood donors.
      ,
      • Davis A.R.
      • Brotchie H.L.
      • Mundkur B.A.
      • Ismary S.L.
      Transient hepatitis B surface antigenemia in a blood donor after a combination hepatitis A and B vaccine.
      ]. As a result blood donation within a month from receiving HBV vaccination is discouraged.

      2.2 Anti-HBc testing

      Anti-HBc screening for blood donation was initially introduced in the mid 1980s as a surrogate marker for non-A, non-B hepatitis. The 40% efficacy was made totally redundant with the implementation of specific antibodies to hepatitis C virus. After being argued as useful to blood safety as a “lifestyle” marker targeting homosexual men and intravenous drug abusers, it was maintained where implemented as improving HBV safety.
      Several studies conducted in Europe and in North America showed that approximately 90% of blood donors carrying anti-HBc also carried anti-HBs signalling recovered HBV infection with a frequency of approximately 90% [
      • Allain J.P.
      • Candotti D.
      • Soldan K.
      • Sarkodie F.
      • Phelps B.
      • Giachetti C.
      • et al.
      The risk of hepatitis B virus infection by transfusion in Kumasi, Ghana.
      ]. The remaining 10% carried either false-positive anti-HBc in a relatively high proportion due to poor assay specificity or true anti-HBc [
      • Roth W.K.
      • Seifried E.
      The German experience with NAT.
      ,
      • Kleinman S.H.
      • Kuhns M.C.
      • Todd D.S.
      • Glynn S.A.
      • McNamara A.
      • DiMarco A.
      • et al.
      Frequency of HBV DNA detection in US blood donors testing positive for the presence of anti-HBc: implications for transfusion transmission and donor screening.
      ]. These samples called “anti-HBc only” may originate either from recovered infections having lost detectable anti-HBs or from late stage chronic infections having lost detectable HBsAg. Evidence of a secondary anti-HBs response after a single dose of HBV vaccine indicated that a large proportion of anti-HBc-only donors had indeed recovered from the infection indicated by activable memory B cells [
      • Schifman R.B.
      • Rivers S.L.
      • Sampliner R.E.
      • Krammes J.E.
      Significance of isolated hepatitis B core antibody in blood donors.
      ,
      • Almeida Neto C.
      • Strauss E.
      • Sabino E.C.
      • Sucupira M.C.
      • Chamone D.A.
      Significance of isolated hepatitis B core antibody in blood donors from São Paulo.
      ]. The issue was further complicated by detecting low levels of HBV DNA not only in anti-HBc only donations but also in some units carrying low-level anti-HBs.
      In donor populations with low prevalence of anti-HBc, deferring all reactive donors was considered affordable in terms of donation loss and more economical than introducing anti-HBs testing to differentiate between presumably non-infectious (anti-HBs ⩾100 IU/L) and potentially infectious donations (no anti-HBs or anti-HBs <100 IU/L). This strategy was not defendable in areas of higher prevalence where deferring anti-HBc reactive units affected negatively the blood supply too severely and at a non-affordable cost. The strategies left open to these areas were either a serologic testing algorithm with anti-HBc followed by anti-HBs or implementation of highly sensitive HBV DNA screening. The latter was adopted in affluent countries in Mediterranean Europe and Poland as well as in Singapore, Hong Kong, Taiwan and Thailand in Eastern Asia or in South Africa [

      Vermeulen M, Lelie N, Sykes W, Crookes R, Swanevelder J, Gaggia L, et al. Impact of individual-donation nucleic acid testing on risk of human immunodeficiency virus, hepatitis B virus, and hepatitis C virus transmission by blood transfusion in South Africa. Transfusion 2009 Feb 27. [Epub ahead of print].

      ,
      • Brojer E.
      • Grabarczyk P.
      • Liszewski G.
      • Mikulska M.
      • Allain J.P.
      • Letowska M.
      • et al.
      Characterization of HBV DNA+/HBsAg− blood donors in Poland identified by triplex NAT.
      ,
      • Velati C.
      • Romano L.
      • Fomiatti L.
      • Baruffi L.
      • Zanetti A.R.
      SIMTI Research Group
      Impact of nucleic acid testing for hepatitis B virus, hepatitis C virus, and human immunodeficiency virus on the safety of blood supply in Italy: a 6-year survey.
      ,
      • Margaritis A.R.
      • Brown S.M.
      • Seed C.R.
      • Kiely P.
      • D’Agostino B.
      • Keller A.J.
      Comparison of two automated nucleic acid testing systems for simultaneous detection of human immunodeficiency virus and hepatitis C virus RNA and hepatitis B virus DNA.
      ,
      • Nantachit N.
      • Thaikruea L.
      • Thongsawat S.
      • Leetrakool N.
      • Fongsatikul L.
      • Sompan P.
      • et al.
      Evaluation of a multiplex human immunodeficiency virus-1, hepatitis C virus, and hepatitis B virus nucleic acid testing assay to detect viremic blood donors in northern Thailand.
      ,
      • Li L.
      • Chen P.J.
      • Chen M.H.
      • Chak K.F.
      • Lin K.S.
      • Lin Tsai S.J.
      A pilot study for screening blood donors in Taiwan by nucleic acid amplification technology: detecting occult hepatitis B virus infections and closing the serologic window period for hepatitis C virus.
      ]. In less affluent areas, the debate remains open.

      2.3 HBV nucleic acid testing (NAT)

      In the past five years, HBV DNA detection assays that combined simultaneous detection of human immunodeficiency virus RNA, hepatitis C virus RNA, and HBV DNA (“multiplex” NAT assays) and corresponding automated testing platforms have made HBV NAT blood screening feasible. Commercial assays based on PCR (Cobas TaqScreen multiplex test; Roche Molecular System) and on TMA (Procleix® Ultrio™ Assay; Novartis/Chiron Blood Testing) showed specificity of 99.9% and 99.8%, and sensitivity of ∼8 IU/mL (∼40 geq/mL) and ∼12 IU/mL (∼60 geq/mL), respectively [
      • Biswas R.
      • Tabor E.
      • Hsia C.C.
      • Wright D.J.
      • Laycock M.E.
      • Fiebig E.W.
      • et al.
      Comparative sensitivity of HBV NATs and HBsAg assays for detection of acute HBV infection.
      ,
      • Margaritis A.R.
      • Brown S.M.
      • Seed C.R.
      • Kiely P.
      • D’Agostino B.
      • Keller A.J.
      Comparison of two automated nucleic acid testing systems for simultaneous detection of human immunodeficiency virus and hepatitis C virus RNA and hepatitis B virus DNA.
      ]. Such high sensitivity allows HBV NAT to significantly reduce the WP left by the most sensitive HBsAg tests. However, the ability of NAT to reduce the WP depends not only on the sensitivity of both the molecular and serological tests, but also on the sample volume (200 or 500 μl) as well as the dilution factor introduced by pooling samples [
      • Biswas R.
      • Tabor E.
      • Hsia C.C.
      • Wright D.J.
      • Laycock M.E.
      • Fiebig E.W.
      • et al.
      Comparative sensitivity of HBV NATs and HBsAg assays for detection of acute HBV infection.
      ,
      • Matsumoto C.
      • Tadokoro K.
      • Fujimura K.
      • Hirakawa S.
      • Mitsunaga S.
      • Juji T.
      Analysis of HBV infection after blood transfusion in Japan through investigation of a comprehensive donor specimen repository.
      ,
      • Sato S.
      • Ohhashi W.
      • Ihara H.
      • Sakaya S.
      • Kato T.
      • Ikeda H.
      Comparison of the sensitivity of NAT using pooled donor samples for HBV and that of a serologic HBsAg assay.
      ,
      • Yotsuyanagi H.
      • Yasuda K.
      • Moriya K.
      • Shintani Y.
      • Fujie H.
      • Tsutsumi T.
      • et al.
      Frequent presence of HBV in the sera of HBsAg-negative, anti-HBc-positive blood donors.
      ,
      • Koppelman M.H.G.
      • Sjerps M.C.
      • Reesink H.W.
      • Cuypers H.T.M.
      Evaluation of COBAS AmpliPrep nucleic acid extraction in conjunction with COBAS AmpliScreen HBV DNA, HCV RNA and HIV-1 RNA amplification and detection.
      ]. Comparing seven HBsAg assays and seven NAT assays (three individual donor [ID] NAT and four minipool [MP] of 16 or 24 donors NAT tests) on acute-phase seroconversion panels, Biswas and colleagues showed that MP NAT and ID NAT reduced the HBV WP by 9–11 days and 25–36 days, respectively, compared to currently licensed HBsAg tests [
      • Biswas R.
      • Tabor E.
      • Hsia C.C.
      • Wright D.J.
      • Laycock M.E.
      • Fiebig E.W.
      • et al.
      Comparative sensitivity of HBV NATs and HBsAg assays for detection of acute HBV infection.
      ]. This leaves a WP of 40–50 days and 15–34 days with MP and ID HBV NAT, respectively.
      Beyond shortening the WP, NAT screening, particularly in individual units, has uncovered a relatively large number of HBsAg-negative “occult” HBV infection or carriage [
      • Allain J.P.
      Occult hepatitis B virus infection: implications in transfusion.
      ,
      • Hollinger F.B.
      Hepatitis B virus infection and transfusion medicine: science and the occult.
      ]. On the basis of the HBV antibody profile, OBI may be stratified into seropositive OBI (anti-HBc and/or anti-HBs positive) and seronegative OBI (anti-HBc and anti-HBs-negative) [
      • Raimondo G.
      • Allain J.P.
      • Brunetto M.R.
      • Buendia M.A.
      • Chen D.S.
      • Colombo M.
      • et al.
      Statements from the Taormina expert meeting on occult hepatitis B virus infection.
      ]. Potential biological explanations for seropositive OBI include the chronic carrier state in which HBsAg has declined over years to a sub-detectable level. OBIs are mainly found in older donors, nearly 100% carry anti-HBc, and approximately 50% also carry anti-HBs suggesting that OBIs occur largely in individuals having recovered from the infection but unable to develop a totally effective immune control [
      • Candotti D.
      • Grabarczyk P.
      • Ghiazza P.
      • Roig R.
      • Casamitjana N.
      • Iudicone P.
      • et al.
      Characterization of occult hepatitis B virus from blood donors carrying genotype A2 or genotype D strains.
      ]. Finally, mutations in the HBV genome affecting viral replication, S antigen production or detection may account for OBI [
      • Weber B.
      Genetic variability of the S gene of hepatitis B virus: clinical and diagnostic impact.
      ,
      • Marusawa H.
      • Uemoto S.
      • Hijikata M.
      • Ueda Y.
      • Tanaka K.
      • Shimotohno K.
      • et al.
      Latent hepatitis B virus infection in healthy individuals with antibodies to hepatitis B core antigen.
      ,
      • Hass M.
      • Hannoun C.
      • Kalinina T.
      • Sommer G.
      • Manegold C.
      • Gunther S.
      Functional analysis of hepatitis B virus reactivating in hepatitis B surface antigen-negative individuals.
      ].
      Seronegative or primary OBIs might have either progressively lost HBV-specific antibodies or are antibody-negative from the beginning of the infection. In the absence of systematic DNA screening and follow-up investigations in seronegative individuals, very limited data support primary occult carriage and the true frequency of this condition remains unknown. One case was identified in a look-back study for post-transfusion hepatitis B [
      • Baginski I.
      • Chemin I.
      • Hantz O.
      • Pichoud C.
      • Jullien A.M.
      • Chevre J.C.
      • et al.
      Transmission of serologically silent hepatitis B virus along with hepatitis C virus in two cases of posttransfusion hepatitis.
      ]. Recently, Manzini and colleagues reported a blood donor who tested HBV NAT positive but did not develop detectable HBsAg over a period of 97 days despite anti-HBc and anti-HBs seroconversion [
      • Manzini P.
      • Abate M.L.
      • Valpreda C.
      • Milanesi P.
      • Curti F.
      • Rizzetto M.
      • et al.
      Evidence of acute primary occult hepatitis B virus infection in an Italian repeat blood donor.
      ]. Three cases of OBI in the acute stage have been reported from the Japanese Red Cross but viral loads were >104 copies/mL (≳103 IU/mL) and S escape mutants could not be ruled out in one of the donors [
      • Yoshikawa A.
      • Gotanda Y.
      • Minegishi K.
      • Taira R.
      • Hino S.
      • Tadokoro K.
      • et al.
      Lengths of hepatitis B viremia and antigenemia in blood donors: preliminary evidence of occult (hepatitis B surface antigen-negative) infection in the acute stage.
      ].
      OBIs are usually characterized by very low HBV DNA load in plasma (<200 IU/mL). Consequently, the occurrence of viremia that is near the assay detection limit and the potential for fluctuating HBV viremia in chronically infected persons suggest that some donors with ongoing HBV infection would not be detected using highly sensitive NAT in very small pools (<10 plasmas) or even in individual units [
      • Biswas R.
      • Tabor E.
      • Hsia C.C.
      • Wright D.J.
      • Laycock M.E.
      • Fiebig E.W.
      • et al.
      Comparative sensitivity of HBV NATs and HBsAg assays for detection of acute HBV infection.
      ,
      • Brojer E.
      • Grabarczyk P.
      • Liszewski G.
      • Mikulska M.
      • Allain J.P.
      • Letowska M.
      • et al.
      Characterization of HBV DNA+/HBsAg− blood donors in Poland identified by triplex NAT.
      ,
      • Matsumoto C.
      • Tadokoro K.
      • Fujimura K.
      • Hirakawa S.
      • Mitsunaga S.
      • Juji T.
      Analysis of HBV infection after blood transfusion in Japan through investigation of a comprehensive donor specimen repository.
      ,
      • Manzini P.
      • Abate M.L.
      • Valpreda C.
      • Milanesi P.
      • Curti F.
      • Rizzetto M.
      • et al.
      Evidence of acute primary occult hepatitis B virus infection in an Italian repeat blood donor.
      ,
      • Dow B.C.
      • Peterkin M.A.
      • Green R.H.A.
      • Cameron S.O.
      Hepatitis B virus transmission by blood donation negative for hepatitis B surface antigen, antibody to HBsAg, antibody to hepatitis B core antigen and HBV DNA.
      ,
      • Busch M.P.
      Should HBV DNA NAT replace HBsAg and/or anti-HBc screening of blood donors?.
      ]. This was demonstrated in Japan when NAT was negative in pools of 50 plasmas but positive in pools of 20 [
      • Yugi H.
      • Mizui M.
      • Tanaka J.
      • Yoshizawa H.
      Hepatitis B virus (HBV) screening strategy to ensure the safety of blood for transfusion through a combination of immunological testing and nucleic acid amplification testing – Japanese experience.
      ]. The apparently marginal benefit of MP NAT, the high cost of ID NAT testing and its very low quality-adjusted-life-year benefit estimate have raised questions about the cost-effectiveness of HBV NAT implementation in low prevalence countries [
      • Busch M.P.
      Should HBV DNA NAT replace HBsAg and/or anti-HBc screening of blood donors?.
      ,
      • Jackson B.R.
      • Busch M.P.
      • Stramer S.L.
      • AuBuchon J.P.
      The cost-effectiveness of NAT for HIV, HCV, and HBV in whole-blood donations.
      ]. These arguments do not apply in countries with higher HBV prevalence [
      • Owusu-Ofori S.
      • Temple J.
      • Sarkodie F.
      • Anokwa M.
      • Candotti D.
      • Allain J.P.
      Predonation screening of blood donors with rapid tests: implementation and efficacy of a novel approach to blood safety in resource-poor settings.
      ,
      • Busch M.
      • Walderhaug M.
      • Custer B.
      • Allain J.P.
      • Reddy R.
      • McDonough B.
      Risk assessment and cost-effectiveness/utility analysis.
      ]. It is unlikely that HBV NAT will replace current serological testing studies since up to 15% of HBsAg-confirmed-positive anti-HBc-positive donations test negative for HBV DNA even by ID-NAT [
      • Allain J.P.
      • Candotti D.
      • Soldan K.
      • Sarkodie F.
      • Phelps B.
      • Giachetti C.
      • et al.
      The risk of hepatitis B virus infection by transfusion in Kumasi, Ghana.
      ,

      Vermeulen M, Lelie N, Sykes W, Crookes R, Swanevelder J, Gaggia L, et al. Impact of individual-donation nucleic acid testing on risk of human immunodeficiency virus, hepatitis B virus, and hepatitis C virus transmission by blood transfusion in South Africa. Transfusion 2009 Feb 27. [Epub ahead of print].

      ,
      • Kuhns M.C.
      • Kleinman S.H.
      • McNamara A.L.
      • Rawal B.
      • Glynn S.
      • Busch M.P.
      Lack of correlation between HBsAg and HBV DNA levels in blood donors who test positive for HBsAg and anti-HBc: implications for future HBV screening policy.
      ].

      2.4 Additional developments to potentially reduce HBV transfusion transmission

      Viral inactivation methods and large-scale HBV vaccination programs have the potential to reduce HBV transfusion transmission. Viral inactivation technologies are applied to plasma and platelet concentrates but still need development to be applied to red cell components or whole blood. A decrease of HBV infection incidence was observed following HBV vaccine implementation in many countries with moderate/high HBV endemicity [
      • Nardone A.
      • Anastassopoulou C.G.
      • Theeten H.
      • Kriz B.
      • Davidkin I.
      • Thierfelder W.
      • et al.
      A comparison of hepatitis B seroepidemiology in ten European countries.
      ,
      • Ni Y.H.
      • Huang L.M.
      • Chang M.H.
      • Yen C.J.
      • Lu C.Y.
      • You S.L.
      • et al.
      Two decades of universal hepatitis B vaccination in Taiwan: impact and implication for future strategies.
      ,
      • Chang M.W.
      Impact of hepatitis B vaccination on hepatitis B disease and nucleic acid testing in high-prevalence populations.
      ]. However, it may take many years to decrease HBV prevalence among blood donors as the vaccine is usually given to newborns, but also in some programs to adolescents and at-risk health-care workers. Pereira and colleagues reported the disappearance of HBV DNA in the serum of patients with OBI after immunization with an HBsAg vaccine; the durability of the response could not be ascertained [
      • Pereira J.S.F.
      • Goncales N.S.L.
      • Silva C.
      • Lazarini M.S.K.
      • Pavan M.H.P.
      • Fais V.C.
      • et al.
      HBV vaccination of HCV-infected patients with occult HBV infection and anti-HBc-positive blood donors.
      ]. Vaccination however may favour the development of escape mutants. Anti-HBs in vaccinated people become undetectable over time and they are susceptible to HBV infection, and up to 5% of vaccinated individuals do not respond [
      • Singh H.
      • Pradhan M.
      • Singh R.L.
      • Phadke S.
      • Naik S.R.
      • Aggarwal R.
      • et al.
      High frequency of hepatitis B virus infection in patients with β-thalassemia receiving multiple transfusions.
      ].

      3. Estimation of HBV residual transfusion transmission risk

      The risk of transfusion-transmitted infections has been widely estimated by using the incidence-window period model [
      • Coste J.
      • Reesink H.W.
      • Engelfriet C.P.
      • Laperche S.
      • Brown S.
      • Busch M.P.
      • et al.
      Implementation of donor screening for infectious agents transmitted by blood by nucleic acid technology: update to 2003.
      ]. This model estimates the risk by multiplying the incidence of new infection by the average time interval during which a newly infected donor is capable of transmitting the infection [
      • Kleinman S.H.
      • Busch M.P.
      Assessing the impact of HBV NAT on window period reduction and residual risk.
      ]. However, the length of the WP varies considerably depending on the screening strategy as discussed above, and whether all WP donations are considered infectious or whether the “eclipse” phase preceding the ramp-up phase is considered infectious. Recently, Busch and colleagues proposed a modified residual risk model using an infectious WP of 38.3 days derived from a HBV doubling time of 2.6 days and assuming that one infused HBV copy will cause infection [
      • Busch M.P.
      • Glynn S.A.
      • Stramer S.L.
      • Strong D.M.
      • Caglioti S.
      • Wright D.J.
      • et al.
      A new strategy for estimating risks of transfusion-transmitted viral infections based on rates of detection of recently infected donors.
      ]. The second critical parameter is the incidence of infection that is directly measured as the number of newly infected (seroconverting) donors divided by the observed person-years at risk. This applies only to repeat donors who made more than one donation during the study period, and it may underestimate the risk as first time donors might be at greater risk of infection than repeat donors [
      • Van der Bij A.K.
      • Coutinho R.A.
      • van der Poel C.L.
      Surveillance of risk profiles among new and repeat blood donors with transfusion-transmissible infections from 1995 through 2003 in the Netherlands.
      ]. The most common approach is to measure seroconversion to HBsAg despite the rapid disappearance of this marker in a few months after infection in 95% of immunocompetent adults [
      • Yoshikawa A.
      • Gotanda Y.
      • Minegishi K.
      • Taira R.
      • Hino S.
      • Tadokoro K.
      • et al.
      Lengths of hepatitis B viremia and antigenemia in blood donors: preliminary evidence of occult (hepatitis B surface antigen-negative) infection in the acute stage.
      ]. Therefore, a newly infected donor would not be identified as such if HBsAg is cleared from the blood between donations and true HBV infection incidence will be underestimated. To resolve this issue, an adjustment factor was calculated [
      • Korelitz J.J.
      • Busch M.P.
      • Kleinman S.H.
      • Williams A.E.
      • Gilcher R.O.
      • Ownby H.E.
      • et al.
      A method for estimating hepatitis B virus incidence rates in volunteer blood donors. National Heart, Lung, and Blood Institute Retrovirus Epidemiology Donor Study.
      ]. Different adjustment factors apply to different donor populations, and prevalence might not accurately reflect the incidence of transfusion-transmissible viral infection. Other influencing factors such as test or process errors, mutant viruses that are not detected by blood donation screening, and OBI are not considered in the model [
      • Janssen M.P.
      • Cator E.A.
      • van der Poel C.L.
      • Schaasberg W.P.
      • Bonsel G.J.
      • van Hout B.A.
      Monitoring viral incidence rates: tools for the implementation of European Union regulations.
      ]. Residual risk estimates reported from different countries are summarized in Table 1. Data comparison should be undertaken with caution since some of the listed countries perform anti-HBc testing in the whole donor population or in particular subsets of donors. In countries not performing anti-HBc testing, seropositive-OBI donors represent a substantial increment in the transfusion transmission risk. Despite all these limitations, the residual risk estimates provided seem to have some validity as they tend to parallel the rates of HBV endemicity. The residual risk per million donations is 0.69–8.69, 7.5–15.8, and 30.6–200 in areas of low, moderate, and high endemicity, respectively (Table 1).
      Table 1Estimated residual risk of transfusion-transmitted HBV infection (per million donations from repeat donors).
      CountryHBV endemicityHBV RR without HBV NATAnti-HBc screeningReferences
      EnglandLow1.66No
      • Soldan K.
      • Davison K.
      • Dow B.
      Estimates of the frequency of HBV, HCV, and HIV infectious donations entering the blood supply in the United Kingdom, 1996 to 2003..
      BelgiumLow5.0Yes/no
      Anti-HBc screening in first-time blood donors.
      • Coste J.
      • Reesink H.W.
      • Engelfriet C.P.
      • Laperche S.
      • Brown S.
      • Busch M.P.
      • et al.
      Implementation of donor screening for infectious agents transmitted by blood by nucleic acid technology: update to 2003.
      FranceLow0.69Yes
      • Laperche S.
      • Maniez M.
      • Barlet V.
      • El Ghouzzi M.-H.
      • Le Vacon F.
      • Levayer T.
      • et al.
      A revised method for estimating hepatitis B virus transfusion residual risk based on antibody to hepatitis B core antigen incident cases.
      The NetherlandsLow2.1No
      • Coste J.
      • Reesink H.W.
      • Engelfriet C.P.
      • Laperche S.
      • Brown S.
      • Busch M.P.
      • et al.
      Implementation of donor screening for infectious agents transmitted by blood by nucleic acid technology: update to 2003.
      FinlandLow2.04No
      • Coste J.
      • Reesink H.W.
      • Engelfriet C.P.
      • Laperche S.
      • Brown S.
      • Busch M.P.
      • et al.
      Implementation of donor screening for infectious agents transmitted by blood by nucleic acid technology: update to 2003.
      GermanyLow4.35Yes/no
      Limited anti-HBc screening on a voluntary basis.
      • Offergeld R.
      • Faensen D.
      • Ritter S.
      • Hamouda O.
      Human immunodeficiency virus, hepatitis C and hepatitis B infections among blood donors in Germany 2000–2002: risk of virus transmission and the impact of nucleic acid amplification testing.
      SwitzerlandLow8.69No
      • Niederhauser C.
      • Schneider P.
      • Fopp M.
      • Ruefer A.
      • Levy G.
      Incidence of viral markers and evaluation of the estimated risk in the Swiss blood donor population from 1996 to 2003.
      CanadaLow6.55Yes
      Anti-HBc screening implemented in 2005.
      • O’Brien S.
      • Yi Q.-L.
      • Fan W.
      • Scalia V.
      • Kleinman S.H.
      • Vamvakas E.C.
      Current incidence and estimated residual risk of transfusion-transmitted infections in donations made to Canadian Blood Services.
      USALow2.05–4.88Yes
      • Dodd R.Y.
      • Notari 4th, E.P.
      • Stramer S.L.
      Current prevalence and incidence of infectious disease markers and estimated window-period risk in the American Red Cross blood donor population.
      ,
      • Kleinman S.H.
      • Strong D.M.
      • Tegtmeier G.G.E.
      • Holland P.V.
      • Gorlin J.B.
      • Cousins C.R.
      • et al.
      Hepatitis B virus (HBV) DNA screening of blood donations in minipools with the COBAS AmpliScreen HBV test.
      AustraliaLow0.75Yes/no
      Anti-HBc screening in donors with a history of hepatitis.
      • Seed C.R.
      • Kiely P.
      • Keller A.J.
      Residual risk of transfusion transmitted human immunodeficiency virus, hepatitis B virus, hepatitis C virus and human T lymphotrophic virus.
      GreeceModerate7.5No
      • Coste J.
      • Reesink H.W.
      • Engelfriet C.P.
      • Laperche S.
      • Brown S.
      • Busch M.P.
      • et al.
      Implementation of donor screening for infectious agents transmitted by blood by nucleic acid technology: update to 2003.
      ItalyModerate13.9–15. 8No
      • Coste J.
      • Reesink H.W.
      • Engelfriet C.P.
      • Laperche S.
      • Brown S.
      • Busch M.P.
      • et al.
      Implementation of donor screening for infectious agents transmitted by blood by nucleic acid technology: update to 2003.
      ,
      • Tosti M.E.
      • Solinas S.
      • Prati D.
      • Salvaneschi L.
      • Manca M.
      • Francesconi M.
      • et al.
      An estimate of the current risk of transmitting blood–borne infections through blood transfusion in Italy.
      SpainModerate9.78No
      • Alvarez do Barrio M.
      • Gonzalez Diez R.
      • Hernandez Sanchez J.M.
      • Oyonarte Gomez S.
      Residual risk of transfusion-transmitted viral infections in Spain, 1997–2002, and impact of nucleic acid testing.
      ChinaHigh30.6–57.1No
      • Shang G.
      • Seed C.R.
      • Wang F.
      • Nie D.
      • Farrugia A.
      Residual risk of transfusion-transmitted viral infections in Shenzhen, China, 2001 through 2004.
      Hong KongHigh200No
      • Coste J.
      • Reesink H.W.
      • Engelfriet C.P.
      • Laperche S.
      • Brown S.
      • Busch M.P.
      • et al.
      Implementation of donor screening for infectious agents transmitted by blood by nucleic acid technology: update to 2003.
      a Anti-HBc screening in first-time blood donors.
      b Limited anti-HBc screening on a voluntary basis.
      c Anti-HBc screening implemented in 2005.
      d Anti-HBc screening in donors with a history of hepatitis.
      The incidence of anti-HBc seroconversion has been proposed as a modifier of the WP-based model resulting in a reduction of risk from 0.69 to 0.49 [
      • Laperche S.
      • Maniez M.
      • Barlet V.
      • El Ghouzzi M.-H.
      • Le Vacon F.
      • Levayer T.
      • et al.
      A revised method for estimating hepatitis B virus transfusion residual risk based on antibody to hepatitis B core antigen incident cases.
      ]. This adjustment appears legitimate but its reliability highly depends on the criteria used to identify anti-HBc seroconversion [
      • Allain J.P.
      Estimation of HBV transfusion risk.
      ]. Measuring the incidence of anti-HBc seroconversion may overestimate the HBV infection incidence related to the poor specificity of anti-HBc assays and the lack of confirmatory assays [
      • Schmidt M.
      • Nubling C.M.
      • Scheiblauer H.
      • Chudy M.
      • Walch L.A.
      • Seifried E.
      • et al.
      Anti-HBc screening of blood donors: a comparison of nine anti-HBc tests.
      ]. Laperche and colleagues proposed to support anti-HBc incidence by the concomitant detection of anti-HBe, anti-HBs in the absence of vaccination, and HBV DNA when implemented. Recent data obtained in European blood donors indicates that HBV DNA-positive/anti-HBc-positive without anti-HBe is as or more frequent than associated with anti-HBe [
      • Brojer E.
      • Grabarczyk P.
      • Liszewski G.
      • Mikulska M.
      • Allain J.P.
      • Letowska M.
      • et al.
      Characterization of HBV DNA+/HBsAg− blood donors in Poland identified by triplex NAT.
      ,
      • Schmidt M.
      • Nubling C.M.
      • Scheiblauer H.
      • Chudy M.
      • Walch L.A.
      • Seifried E.
      • et al.
      Anti-HBc screening of blood donors: a comparison of nine anti-HBc tests.
      ,
      • Hennig H.
      • Puchta I.
      • Luhm J.
      • Schlenke P.
      • Goerg S.
      • Kirchner H.
      Frequency and load of hepatitis B virus DNA in first-time blood donors with antibodies to hepatitis B core antigen.
      ,
      • Vitale F.
      • Tramuto F.
      • Orlando A.
      • Vizzini G.
      • Meli V.
      • Cerame G.
      • et al.
      Can the serological status of anti-HBc alone be considered a sentinel marker for detection of occult HBV infection?.
      ].
      Another method proposes to calculate the incident infection rate as the number of NAT-yield donations divided by the number of person-years [
      • Kleinman S.H.
      • Busch M.P.
      Assessing the impact of HBV NAT on window period reduction and residual risk.
      ,
      • Busch M.P.
      • Glynn S.A.
      • Stramer S.L.
      • Strong D.M.
      • Caglioti S.
      • Wright D.J.
      • et al.
      A new strategy for estimating risks of transfusion-transmitted viral infections based on rates of detection of recently infected donors.
      ,
      • O’Brien S.
      • Yi Q.-L.
      • Fan W.
      • Scalia V.
      • Kleinman S.H.
      • Vamvakas E.C.
      Current incidence and estimated residual risk of transfusion-transmitted infections in donations made to Canadian Blood Services.
      ]. This method allows the determination of the incidence rate in all donations, and occult HBV carriage will be included in the calculation of the residual risk. This method highly depends on the accuracy of the estimation of HBV NAT yield. Indeed, HBV DNA yield appears directly related not only to the analytical sensitivity and pool size of the HBV NAT assay, but also to the analytical sensitivity of the HBsAg used for screening and to the general HBV prevalence in the donor population. HBV NAT yields reported from countries with low, moderate, and high HBsAg prevalence range between 1:4000 and 1:730,000 [
      • Roth W.K.
      • Seifried E.
      The German experience with NAT.
      ,
      • Kleinman S.H.
      • Strong D.M.
      • Tegtmeier G.G.E.
      • Holland P.V.
      • Gorlin J.B.
      • Cousins C.R.
      • et al.
      Hepatitis B virus (HBV) DNA screening of blood donations in minipools with the COBAS AmpliScreen HBV test.
      ,
      • Hennig H.
      • Puchta I.
      • Luhm J.
      • Schlenke P.
      • Goerg S.
      • Kirchner H.
      Frequency and load of hepatitis B virus DNA in first-time blood donors with antibodies to hepatitis B core antigen.
      ,
      • Chevrier M.C.
      • St-Louis M.
      • Perreault J.
      • Caron B.
      • Castilloux C.
      • Laroche J.
      • et al.
      Detection and characterization of hepatitis B virus of anti-hepatitis B core antigen-reactive blood donors in Quebec with an in-house nucleic acid testing assay.
      ,
      • O’Brien S.F.
      • Fearon M.A.
      • Yi Q.-L.
      • Fan W.
      • Scalia V.
      • Muntz I.R.
      • et al.
      Hepatitis B virus DNA-positive, hepatitis B surface antigen-negative blood donations intercepted by anti-hepatitis B core antigen testing: the Canadian Blood Services experience.
      ,
      • Hourfar M.K.
      • Jork C.
      • Schottstedt V.
      • Weber-Schehl M.
      • Brixner V.
      • Busch M.P.
      • et al.
      Experience of German red cross blood donor services with nucleic acid testing: results of screening more than 30 million blood donations for human immunodeficiency virus-1, hepatitis C virus, and hepatitis B virus.
      ,
      • Stramer S.L.
      Current risks of transfusion-transmitted agents.
      ], 1:4000 and 1:20,300 [
      • Brojer E.
      • Grabarczyk P.
      • Liszewski G.
      • Mikulska M.
      • Allain J.P.
      • Letowska M.
      • et al.
      Characterization of HBV DNA+/HBsAg− blood donors in Poland identified by triplex NAT.
      ,
      • Velati C.
      • Romano L.
      • Fomiatti L.
      • Baruffi L.
      • Zanetti A.R.
      SIMTI Research Group
      Impact of nucleic acid testing for hepatitis B virus, hepatitis C virus, and human immunodeficiency virus on the safety of blood supply in Italy: a 6-year survey.
      ,
      • Ramia S.
      • Ramlawi F.
      • Kanaan M.
      • Klayme S.
      • Naman R.
      Frequency and significance of antibodies against hepatitis B core (anti-HBc) antigen as the only serological marker for hepatitis B infection in Lebanese blood donors.
      ,
      • Katsoulidou A.
      • Moschidis Z.
      • Sypsa V.
      • Chini M.
      • Papatheodoridis G.V.
      • Tassopoulos N.C.
      • et al.
      Analytical and clinical sensitivity of the Procleix Ultrio HIV-1/HCV/HBV assay in samples with a low viral load.
      ,
      • Manzini P.
      • Girotto M.
      • Borsotti R.
      • Giachino O.
      • Guaschino R.
      • Lanteri M.
      • et al.
      Italian blood donors with anti-HBc and occult hepatitis B virus infection.
      ], and 1:192 and 1:5200 [
      • Owusu-Ofori S.
      • Temple J.
      • Sarkodie F.
      • Anokwa M.
      • Candotti D.
      • Allain J.P.
      Predonation screening of blood donors with rapid tests: implementation and efficacy of a novel approach to blood safety in resource-poor settings.
      ,
      • Allain J.P.
      • Candotti D.
      • Soldan K.
      • Sarkodie F.
      • Phelps B.
      • Giachetti C.
      • et al.
      The risk of hepatitis B virus infection by transfusion in Kumasi, Ghana.
      ,

      Vermeulen M, Lelie N, Sykes W, Crookes R, Swanevelder J, Gaggia L, et al. Impact of individual-donation nucleic acid testing on risk of human immunodeficiency virus, hepatitis B virus, and hepatitis C virus transmission by blood transfusion in South Africa. Transfusion 2009 Feb 27. [Epub ahead of print].

      ,
      • Margaritis A.R.
      • Brown S.M.
      • Seed C.R.
      • Kiely P.
      • D’Agostino B.
      • Keller A.J.
      Comparison of two automated nucleic acid testing systems for simultaneous detection of human immunodeficiency virus and hepatitis C virus RNA and hepatitis B virus DNA.
      ,
      • Nantachit N.
      • Thaikruea L.
      • Thongsawat S.
      • Leetrakool N.
      • Fongsatikul L.
      • Sompan P.
      • et al.
      Evaluation of a multiplex human immunodeficiency virus-1, hepatitis C virus, and hepatitis B virus nucleic acid testing assay to detect viremic blood donors in northern Thailand.
      ,
      • Li L.
      • Chen P.J.
      • Chen M.H.
      • Chak K.F.
      • Lin K.S.
      • Lin Tsai S.J.
      A pilot study for screening blood donors in Taiwan by nucleic acid amplification technology: detecting occult hepatitis B virus infections and closing the serologic window period for hepatitis C virus.
      ,
      • Makroo R.N.
      • Choudhury N.
      • Jagannathan L.
      • Parihar-Malhotra M.
      • Raina V.
      • Chaudhary R.K.
      • et al.
      Multicenter evaluation of individual donor nucleic acid testing (NAT) for simultaneous detection of human immunodeficiency virus-1 & hepatitis B & C viruses in Indian blood donors.
      ], respectively. As studies conducted in different countries used different serological and NAT assays with variable pool sizes, and were performed in selected (repeat, first time, or anti-HBc-positive donors) or unselected populations of blood donors, comparison of results is difficult. Despite these limitations, HBV DNA yield increases with HBsAg and anti-HBc prevalence, irrespective of MP- or ID-NAT screening or anti-HBc status [
      • Comanor L.
      • Holland P.
      Hepatitis B virus blood screening: unfinished agendas.
      ,
      • Liu C.J.
      • Chen D.S.
      • Chen P.J.
      Epidemiology of HBV infection in Asian blood donors: emphasis on occult HBV infection and the role of NAT.
      ]. In low-prevalence Germany, implementation of HBV NAT (essentially in-house assay) in pool of 96 submitted to prolonged high-speed centrifugation or individual unit resulted in residual risks of 1.61 and 1.23 per million donations, respectively, compared to 4.35 per million without NAT [
      • Offergeld R.
      • Faensen D.
      • Ritter S.
      • Hamouda O.
      Human immunodeficiency virus, hepatitis C and hepatitis B infections among blood donors in Germany 2000–2002: risk of virus transmission and the impact of nucleic acid amplification testing.
      ]. Similarly, a study conducted in high-prevalence China showed that a residual risk of 30.6 per million donations after HBsAg screening was reduced to 29.0 and 17.4 when NAT was used in pools of 16 and in individual testing, respectively [
      • Shang G.
      • Seed C.R.
      • Wang F.
      • Nie D.
      • Farrugia A.
      Residual risk of transfusion-transmitted viral infections in Shenzhen, China, 2001 through 2004.
      ].

      4. HBV transmission by transfusion

      4.1 Determining the HBV infectious dose(s)

      The estimated residual risk of HBV transfusion transmission remains significantly higher than the risk of either HIV-1 or HCV. Whether residual risk estimates translate into true rate of infection is largely unknown since estimates are generally based on the simplification that all HBV DNA-containing donations are infectious.
      Studies have attempted to address this question by using the chimpanzee model. Genotype A or genotype C inoculum derived from two infected blood donors who were in the pre-acute phase (HBsAg and HBV DNA-positive but anti-HBc-negative) were used to infect two chimpanzees whose pre-acute phase serum samples were then used to infect two other chimpanzees. The estimated minimum HBV copy numbers that could infect 50% of the chimpanzees (CID50) was approximately 10 copies or geq, irrespective of HBV genotype [
      • Komiya Y.
      • Katayama K.
      • Yugi H.
      • Mizui M.
      • Matsukura H.
      • Tomoguri T.
      • et al.
      Minimum infectious dose of hepatitis B virus in chimpanzees and difference in the dynamics of viremia between genotype A and genotype C.
      ]. A similar result was reported from three chimpanzees infected with serum from a HBV genotype A-infected individual in the acute phase of infection [
      • Yugi H.
      • Mizui M.
      • Tanaka J.
      • Yoshizawa H.
      Hepatitis B virus (HBV) screening strategy to ensure the safety of blood for transfusion through a combination of immunological testing and nucleic acid amplification testing – Japanese experience.
      ]. Using three serum inoculae from chronic carriers (HBsAg-positive and anti-HBc-positive), Hsia and colleagues estimated CID50 was 169 geq for genotype A, 3 for genotype C, and 78 for genotype D [
      • Hsia C.C.
      • Purcell R.H.
      • Farshid M.
      • Lachenbruch P.A.
      • Yu M.Y.
      Quantification of hepatitis B virus genomes and infectivity in human serum samples.
      ]. Utilizing a chimeric mouse model tolerating human liver tissue, Japanese investigators determined the HBV infectious dose of a pre-acute and late acute HBV serum required for transmission to be 10 and 100 geq, respectively [
      • Tsuge M.
      • Hiraga N.
      • Takaishi H.
      • Noguchi C.
      • Oga H.
      • Imamura M.
      • et al.
      Infection of human hepatocyte chimeric mouse with genetically engineered hepatitis B virus.
      ,
      • Tabuchi A.
      • Tanaka J.
      • Katayama K.
      • Mizui M.
      • Matsukura H.
      • Yugi H.
      • et al.
      Titration of hepatitis B virus infectivity in the sera of pre-acute and late acute phases of HBV infection: transmission experiments to chimeric mice with human liver repopulated hepatocytes.
      ].
      In humans, HBV transmission was reported from donors in the WP and OBI donors showing HBV DNA load <20 IU/mL (Table 2) [
      • Dow B.C.
      • Peterkin M.A.
      • Green R.H.A.
      • Cameron S.O.
      Hepatitis B virus transmission by blood donation negative for hepatitis B surface antigen, antibody to HBsAg, antibody to hepatitis B core antigen and HBV DNA.
      ,
      • Inaba S.
      • Ito A.
      • Miyata Y.
      • Ishii H.
      • Kajimoto S.
      • Tanaka M.
      • et al.
      Individual nucleic amplification technology does not prevent all hepatitis B virus transmission by blood transfusion.
      ,
      • Satake M.
      • Taira R.
      • Yugi H.
      • Hino S.
      • Kanemitsu K.
      • Ikeda H.
      • et al.
      Infectivity of blood components with low hepatitis B virus DNA levels identified in a lookback program.
      ]. However, in some cases, units from WP and OBI donors were not infectious even though viral load ranging between <20 and >500 IU/mL (<100 and >2500 geq/ml) was transfused [
      • Matsumoto C.
      • Tadokoro K.
      • Fujimura K.
      • Hirakawa S.
      • Mitsunaga S.
      • Juji T.
      Analysis of HBV infection after blood transfusion in Japan through investigation of a comprehensive donor specimen repository.
      ,
      • Inaba S.
      • Ito A.
      • Miyata Y.
      • Ishii H.
      • Kajimoto S.
      • Tanaka M.
      • et al.
      Individual nucleic amplification technology does not prevent all hepatitis B virus transmission by blood transfusion.
      ,
      • Satake M.
      • Taira R.
      • Yugi H.
      • Hino S.
      • Kanemitsu K.
      • Ikeda H.
      • et al.
      Infectivity of blood components with low hepatitis B virus DNA levels identified in a lookback program.
      ,
      • Wang J.T.
      • Lee C.Z.
      • Chen P.J.
      • Wang T.H.
      • Chen D.S.
      Transfusion-transmitted HBV infection in an endemic area: the necessity of more sensitive screening for HBV carriers.
      ]. The lack of clear relationship between infectivity and viral load in blood components may be related to immune factors affecting the susceptibility to infection in recipients as discussed below. In addition, HBV infectivity is essentially related to the amount of plasma transfused and the viral load in the product. At equal volume of product, fresh-frozen plasma (FFP) and platelet concentrates (PC) suspended in plasma were 3- to 20-fold more infectious than red cell concentrates containing approximately 20% of plasma.
      Table 2Transfusion transmission of HBV from HBsAg-negative blood donations.
      Only confirmed HBV transfusion-associated transmission were considered.
      ReferenceDonorsProducts transfused
      RBC, red blood cells; FFP, fresh-frozen plasmas; PC, platelet concentrates.
      Transmission casesRecipients anti-HBs (IU/L)
      Anti-HBcHBV DNA (IU/mL)Anti-HBs (IU/L)
      1 International Unit (IU) is equivalent to approximately 5 genome equivalents (geq) or copies for HBV genotype A, subtype adw2.
      HBV statusNb recipientsNb transmission
      • Jongerius J.M.
      • van der Poel C.L.
      • van Leeuwen E.F.
      A simple strategy to look back on posttransfusion hepatitis B in a multitransfused patient.
      Neg.Weak pos.WPPC11NA
      NA, not available.
      RBC11NA
      FFP11NA
      • Matsumoto C.
      • Tadokoro K.
      • Fujimura K.
      • Hirakawa S.
      • Mitsunaga S.
      • Juji T.
      Analysis of HBV infection after blood transfusion in Japan through investigation of a comprehensive donor specimen repository.
      Neg.660WPPlasma11NA
      RBC10NA
      Neg.Neg.WPPC11NA
      Neg.600WPPC11NA
      Neg.160WPPlasma11NA
      Neg.>10WPNA11NA
      Neg.>10WPNA11NA
      Neg.>10WPNA11NA
      Pos.>10NAOBINA11NA
      Pos.>10NAOBINA11NA
      • Dow B.C.
      • Peterkin M.A.
      • Green R.H.A.
      • Cameron S.O.
      Hepatitis B virus transmission by blood donation negative for hepatitis B surface antigen, antibody to HBsAg, antibody to hepatitis B core antigen and HBV DNA.
      Neg.<25WPRBC11NA
      PC11NA
      • Soldan K.
      • Barbara J.A.J.
      • Dow B.C.
      Transfusion-transmitted hepatitis B virus infection in the UK: a small and moving target.
      Neg.Pos.WP11NA
      Neg.Pos.WP11NA
      Neg.Pos.WP11NA
      Neg.Neg.WP1NA
      • Wang J.T.
      • Lee C.Z.
      • Chen P.J.
      • Wang T.H.
      • Chen D.S.
      Transfusion-transmitted HBV infection in an endemic area: the necessity of more sensitive screening for HBV carriers.
      Pos.10–100Neg.OBINA112NA
      • Dreier J.
      • Kroger M.
      • Diekmann J.
      • Gotting C.
      • Kleesiek K.
      Low-level viraemia of hepatitis B virus in an anti-HBc- and anti-HBs-positive blood donor.
      Pos.<10–260Pos.OBIRBC90NA
      (2 534–7 371)FFP20NA
      • Inaba S.
      • Ito A.
      • Miyata Y.
      • Ishii H.
      • Kajimoto S.
      • Tanaka M.
      • et al.
      Individual nucleic amplification technology does not prevent all hepatitis B virus transmission by blood transfusion.
      Weak<10–40Neg.OBIPC106NA
      Pos.NA
      • Gerlich W.H.
      Breakthrough of hepatitis B virus escape mutants after vaccination and virus reactivation.
      Pos.<10Pos.OBI
      Breakthrough of an escape mutant.
      PC650NA
      • Satake M.
      • Taira R.
      • Yugi H.
      • Hino S.
      • Kanemitsu K.
      • Ikeda H.
      • et al.
      Infectivity of blood components with low hepatitis B virus DNA levels identified in a lookback program.
      1 Pos.<20Neg.OBIFFP11NA
      32 Pos.<20–2411 PosOBI17 RBC320NA
      12 Neg.14 FFP, 1NA
      9 Und.PCNA
      11Neg.<20–76WP5 RBC, 41111NA
      FFP, 2 PCNA
      11Neg.<20–60WP5 RBC, 4110NA
      FFP, 2 PCNA
      • Levicnik-Stezinar S.
      • Rahne-Potokar U.
      • Candotti D.
      • Lelie N.
      • Allain J.P.
      Anti-HBs positive occult hepatitis B virus carrier blood infectious in two transfusion recipients.
      Pos.180Pos. (12)OBIFFP11Neg.
      RBC11Neg.
      <1–63Pos.NA20Neg.
      (15–29)
      • Wendel S.
      • Levi J.E.
      • Biagini S.
      • Candotti D.
      • Allain J.-P.
      A probable case of hepatitis B virus transfusion transmission revealed after a 13-month-long window period.
      Neg.>500WPRBC11Pos.
      PC10(12–65)
      Pos.
      (15)
      • Chudy M.
      • Schmidt M.
      • Czudai V.
      • Scheiblauer H.
      • Nick S.
      • Mosebach M.
      • et al.
      Hepatitis B virus genotype G monoinfection and its transmission by blood components.
      Neg.171WPPC11Neg.
      10Pos. (135)
      125211Neg.
      10Pos. (164)
      a Only confirmed HBV transfusion-associated transmission were considered.
      b 1 International Unit (IU) is equivalent to approximately 5 genome equivalents (geq) or copies for HBV genotype A, subtype adw2.
      c RBC, red blood cells; FFP, fresh-frozen plasmas; PC, platelet concentrates.
      d Breakthrough of an escape mutant.
      e NA, not available.

      4.2 Risk of transmission from clinical data

      While HBV transmission from HBsAg-negative donations is supported by several studies since the early 1980s [
      • Hoofnagle J.H.
      • Waggoner J.G.
      Hepatitis A and B virus markers in immune serum globulin.
      ], it is not a frequently reported event, at least in low-prevalence countries, consistent with the small number of WP and occult carriage reported. In the United States, the risk of transfusing a potentially infectious HBsAg-negative/anti-HBc-positive/HBV DNA-positive unit has been reported to be ∼1 in 50,000 donations if all HBV-positive donations were assumed to be infectious [
      • Kleinman S.H.
      • Kuhns M.C.
      • Todd D.S.
      • Glynn S.A.
      • McNamara A.
      • DiMarco A.
      • et al.
      Frequency of HBV DNA detection in US blood donors testing positive for the presence of anti-HBc: implications for transfusion transmission and donor screening.
      ,
      • Kleinman S.H.
      • Strong D.M.
      • Tegtmeier G.G.E.
      • Holland P.V.
      • Gorlin J.B.
      • Cousins C.R.
      • et al.
      Hepatitis B virus (HBV) DNA screening of blood donations in minipools with the COBAS AmpliScreen HBV test.
      ]. However, of 7381 cases of acute hepatitis B reported in 2003, 49 were initially reported as transfusion-associated. Only 10 of those were further confirmed by the Centers for Disease Control and Prevention as acute cases of hepatitis B involving transfused blood products and finally only 1 case could be associated with a single infected donor [
      • Stramer S.L.
      Pooled hepatitis B virus DNA testing by nucleic acid amplification: implementation or not.
      ]. Similar data were reported from Canada, the UK, and Japan [
      • O’Brien S.F.
      • Fearon M.A.
      • Yi Q.-L.
      • Fan W.
      • Scalia V.
      • Muntz I.R.
      • et al.
      Hepatitis B virus DNA-positive, hepatitis B surface antigen-negative blood donations intercepted by anti-hepatitis B core antigen testing: the Canadian Blood Services experience.
      ,
      • Satake M.
      • Taira R.
      • Yugi H.
      • Hino S.
      • Kanemitsu K.
      • Ikeda H.
      • et al.
      Infectivity of blood components with low hepatitis B virus DNA levels identified in a lookback program.
      ,
      • Soldan K.
      • Barbara J.A.J.
      • Dow B.C.
      Transfusion-transmitted hepatitis B virus infection in the UK: a small and moving target.
      ].
      Data summarized in Table 2 indicate that (1) WP and anti-HBs-positive and negative OBI units can transmit HBV; (2) the confirmed HBV transmission rate of WP-derived donations is higher than by occult carriers (81% versus 19%) but may be biased by the large number of Japanese cases identified with a peculiar set of anti-HBc and DNA screening protocol [
      • Satake M.
      • Taira R.
      • Yugi H.
      • Hino S.
      • Kanemitsu K.
      • Ikeda H.
      • et al.
      Infectivity of blood components with low hepatitis B virus DNA levels identified in a lookback program.
      ]; (3) viral transmission can be associated with extremely low level of HBV DNA in anti-HBc-positive-only units (<20 IU/mL) or blood collected during the very early phase of acute infection (eclipse phase) in which neither HBsAg nor HBV DNA is detectable [
      • Matsumoto C.
      • Tadokoro K.
      • Fujimura K.
      • Hirakawa S.
      • Mitsunaga S.
      • Juji T.
      Analysis of HBV infection after blood transfusion in Japan through investigation of a comprehensive donor specimen repository.
      ,
      • Soldan K.
      • Barbara J.A.J.
      • Dow B.C.
      Transfusion-transmitted hepatitis B virus infection in the UK: a small and moving target.
      ]; (4) HBV DNA load is similar in infectious and non-infectious anti-HBc-positive donations, suggesting that viral load is not the only factor for infectivity; and (5) the presence of anti-HBs seems to largely protect from transmission [
      • Satake M.
      • Taira R.
      • Yugi H.
      • Hino S.
      • Kanemitsu K.
      • Ikeda H.
      • et al.
      Infectivity of blood components with low hepatitis B virus DNA levels identified in a lookback program.
      ,
      • Gerlich W.H.
      • Wagner F.F.
      • Chudy M.
      • Holm Harritshoj L.
      • Lattermann A.
      • Wienzek S.
      • et al.
      HBsAg non-reactive HBV infection in blood donors: transmission and pathogenicity.
      ], except in rare cases [
      • Levicnik-Stezinar S.
      • Rahne-Potokar U.
      • Candotti D.
      • Lelie N.
      • Allain J.P.
      Anti-HBs positive occult hepatitis B virus carrier blood infectious in two transfusion recipients.
      ] (Fig. 1).
      Figure thumbnail gr1
      Fig. 1Relationship between HBV DNA load and anti-HBs reactivity in an OBI donor associated with transfusion transmission of HBV (modified from
      [
      • Levicnik-Stezinar S.
      • Rahne-Potokar U.
      • Candotti D.
      • Lelie N.
      • Allain J.P.
      Anti-HBs positive occult hepatitis B virus carrier blood infectious in two transfusion recipients.
      ]
      ). Open and plain circles indicate anti-HBs reactivity (IU/L) and HBV DNA load (IU/mL), respectively. The dashed line indicates absence of HBV DNA testing. HBV transmission is indicated by black vertical arrows; absence of transmission by an open arrow.
      The concomitant presence of anti-HBs with HBV virions in the peripheral blood of donors neutralizes in proportion of antibody titer and ability to recognize surface protein antigens. Experiments in chimpanzees showed no HBV infection in animals transfused with blood from three anti-HBs-positive human plasmas, despite exposure to an HBV DNA dose known to be infectious in the absence of anti-HBs [
      • Prince A.M.
      • Lee D.H.
      • Brotman B.
      Infectivity of blood from PCR-positive, HBsAg-negative, anti-HBs-positive cases of resolved hepatitis B infection.
      ]. The presence of anti-HBs following natural infection, vaccination, or passive immunoprophylaxis prevents de novo HBV infection in transplanted patients receiving anti-HBc-positive livers [
      • Barcena R.
      • Moraleda G.
      • Moreno J.
      • Martin M.D.
      • de Vicente E.
      • Nuno J.
      • et al.
      Prevention of de novo HBV infection by the presence of anti-HBs in transplanted patients receiving core antibody-positive livers.
      ,
      • Dodson S.F.
      Prevention of de novo hepatitis B infection after liver transplantation with allografts from hepatitis B core antibody positive donors.
      ,
      • Roque-Afonso A.M.
      • Feray C.
      • Samuel D.
      • Simoneau D.
      • Roche B.
      • Emile J.F.
      • et al.
      Antibodies to hepatitis B surface antigen prevent viral reactivation in recipients of liver grafts from anti-HBc positive donors.
      ,
      • Roche B.
      • Feray C.
      • Gigou M.
      • Roque-Afonso A.M.
      • Arulnaden J.L.
      • Delvart V.
      • et al.
      HBV DNA persistence 10 years after liver transplantation despite successful anti-HBs passive immunoprophylaxis.
      ]. Consequently, the transfusion of anti-HBc-positive blood with high levels of anti-HBs (>200 IU/L) is allowed in Japan and no post-transfusion cases have been documented from such units [
      • Matsumoto C.
      • Tadokoro K.
      • Fujimura K.
      • Hirakawa S.
      • Mitsunaga S.
      • Juji T.
      Analysis of HBV infection after blood transfusion in Japan through investigation of a comprehensive donor specimen repository.
      ,
      • Sato S.
      • Ohhashi W.
      • Ihara H.
      • Sakaya S.
      • Kato T.
      • Ikeda H.
      Comparison of the sensitivity of NAT using pooled donor samples for HBV and that of a serologic HBsAg assay.
      ,
      • Satake M.
      • Taira R.
      • Yugi H.
      • Hino S.
      • Kanemitsu K.
      • Ikeda H.
      • et al.
      Infectivity of blood components with low hepatitis B virus DNA levels identified in a lookback program.
      ]. Dreier and colleagues reported intermittent low HBV DNA levels (<10–260 IU/mL) over a 7-year period in an HBsAg-negative anti-HBc-positive donor with anti-HBs (>2000 IU/L) but no HBV transmission occurred [
      • Dreier J.
      • Kroger M.
      • Diekmann J.
      • Gotting C.
      • Kleesiek K.
      Low-level viraemia of hepatitis B virus in an anti-HBc- and anti-HBs-positive blood donor.
      ]. Another study described a breakthrough HBV escape variant in a plateletpheresis donor [
      • Gerlich W.H.
      Breakthrough of hepatitis B virus escape mutants after vaccination and virus reactivation.
      ]. Infection occurred three years after vaccination, the donor developed a persistent low-level HBV-infection (HBsAg-negative, anti-HBc-positive, HBV DNA at levels <5 IU/mL) despite a high vaccine-induced anti-HBs response (>1000 IU/L). Lookback of 65 recipients of PC from this donor (∼200 IU/donation) did not reveal HBV transmission.
      The principle of protection by units with high levels of anti-HBs is commonly accepted, although there is no agreement on the threshold level but 100 IU/L is often cited [
      • Grob P.
      • Jilg W.
      • Bornhak H.
      • Gerken G.
      • Gerlich W.
      • Günther S.
      • et al.
      Serological pattern “anti-HBc alone”: report on a workshop.
      ]. No evidence of transmission was found in 131 recipients who were transfused with 97 components containing anti-HBc and anti-HBs at levels <100 IU/L [
      • Allain J.P.
      • Hewitt P.E.
      • Tedder R.S.
      • Williamson L.
      Evidence that anti-HBc but not HBV DNA testing may prevent some HBV transmission by transfusion.
      ]. In contrast, others described five cases of HBV transmission presumably linked to anti-HBc-positive donors: three lacked anti-HBs and two had low level of anti-HBs (probably <10 IU/L) [
      • Kleinman S.H.
      • Kuhns M.C.
      • Todd D.S.
      • Glynn S.A.
      • McNamara A.
      • DiMarco A.
      • et al.
      Frequency of HBV DNA detection in US blood donors testing positive for the presence of anti-HBc: implications for transfusion transmission and donor screening.
      ,
      • Mosley J.W.
      • Stevens C.E.
      • Aach R.D.
      • Hollinger F.B.
      • Mimms L.T.
      • Solomon L.R.
      • et al.
      Donor screening for antibody to hepatitis B core antigen and hepatitis B virus infection in transfusion recipients.
      ]. Recently, one case of an OBI donor with anti-HBs who transmitted to two immunocompetent transfusion recipients of FFP and red blood cells (RBC) was reported [
      • Levicnik-Stezinar S.
      • Rahne-Potokar U.
      • Candotti D.
      • Lelie N.
      • Allain J.P.
      Anti-HBs positive occult hepatitis B virus carrier blood infectious in two transfusion recipients.
      ]. The implicated donation contained anti-HBc, anti-HBs (12 IU/L), and 180 IU/mL of HBV DNA. Previous donations contained 6–10 times less viral DNA than the index donation, anti-HBs levels ranged between 15 and 29 IU/L, and no clinical evidence of HBV transmission was recorded in 14 recipients. It was speculated that the main factor for infectivity was a temporary higher viral load sufficient to overcome the relatively weak neutralizing capacity of a low anti-HBs level. This interpretation was supported by a secondary anti-HBs immune response. This particular case clearly illustrates that the neutralizing capacity of low-level anti-HBs is limited and reinforces the validity of considering anti-HBs below 50–100 IU/L to be poorly protective from infectivity when HBV DNA is present. This factor needs to be considered in triggers to maintain effective post-vaccination protection [
      • Chang M.W.
      Impact of hepatitis B vaccination on hepatitis B disease and nucleic acid testing in high-prevalence populations.
      ,
      • Liu C.J.
      • Lo S.H.
      • Kao J.H.
      • Tseng P.T.
      • Lai M.Y.
      • Ni Y.H.
      • et al.
      Transmission of occult hepatitis B virus by transfusion to adult and pediatric recipients in Taiwan.
      ,
      • Knoll A.
      • Boehm S.
      • Hahn J.
      • Holler E.
      • Jilg W.
      Long-term surveillance of haematopoietic stem cell recipients with resolved hepatitis B: high risk of viral reactivation even in a recipient with a vaccinated donor.
      ,
      • Su F.H.
      • Chen J.D.
      • Cheng S.H.
      • Sung K.Y.
      • Jeng J.J.
      • Chu F.Y.
      Waning-off effect of serum hepatitis B surface antibody amongst Taiwanese university students: 18 years post-implementation of Taiwan’s national hepatitis B vaccination programme.
      ,
      • Van Damme P.
      • Van Herck K.
      A review of the long-term protection after hepatitis A and B vaccination.
      ].
      The immune status of the recipient is another critical factor in transfusion transmission of HBV. After acute HBV infection was diagnosed in a regular apheresis donor, four platelet components recipients were identified; two HBV-naı¨ve were infected but two who were anti-HBs-positive pre-transfusion (135 and 164 IU/L) were not. Several studies indicated that recipients of anti-HBc-positive organs (e.g. liver) developed HBV infection, even if HBV DNA was not detected in the donors’ serum [
      • Roche B.
      • Samuel D.
      • Gigou M.
      • Feray C.
      • Virot V.
      • Schmets L.
      • et al.
      De novo and apparent de novo hepatitis B virus infection after liver transplantation.
      ,
      • Dickson R.C.
      • Wright R.M.
      • Bacchetta M.D.
      • Bodily S.E.
      • Caldwell S.H.
      • Driscoll C.J.
      • et al.
      Quality of life of hepatitis B and C patients after liver transplantation.
      ,
      • Uemoto S.
      • Sugiyama K.
      • Marusawa H.
      • Inomata Y.
      • Asonuma K.
      • Egawa H.
      • et al.
      Transmission of hepatitis B virus from hepatitis B core antibody-positive donors in living related liver transplants.
      ,
      • Kim K.H.
      • Ahn S.H.
      • Chung H.Y.
      • Paik Y.H.
      • Lee K.S.
      • Kim Y.S.
      • et al.
      Hepatitis B virus infection after renal transplantation in the presence of antibody to hepatitis B surface antigen immunity.
      ]. These data suggest an increased susceptibility to HBV infection of transplant patients undergoing intensive immunosuppressive therapy in the absence of prophylactic treatment. This situation can be probably derived from organs to blood components as approximately 50% of recipients of blood components in Western Europe present some degree of immunodeficiency [
      • Llewelyn C.A.
      • Wells A.W.
      • Amin M.
      • Casbard A.
      • Johnson A.J.
      • Ballard S.
      • et al.
      The EASTR study: a new approach to determine the reasons for transfusion in epidemiological studies.
      ]. It was shown that both active and passive neutralizing anti-HBs likely delayed but did not prevent acute infection when the immune system was impaired [
      • Wendel S.
      • Levi J.E.
      • Biagini S.
      • Candotti D.
      • Allain J.-P.
      A probable case of hepatitis B virus transfusion transmission revealed after a 13-month-long window period.
      ].

      4.3 Diagnosis of transfusion-transmitted HBV

      Transfusion transmission can be documented by (1) notifying and testing donors that have been implicated in a case of possible post-transfusion hepatitis B (traceback); (2) notifying and testing recipients after the administration of potentially infectious HBV-containing blood products (lookback); and (3) prospective testing of donor–recipient pairs. Each strategy has its own limitations. No prospective studies have been conducted so far because it requires an extremely large number of patients and high cost.
      The traceback strategy relies primarily on clinical evidence and proper diagnostic of hepatitis B in the recipient. Inaba and colleagues reported three of four cases of acute hepatitis B and two suspected seroconversions that were not recognized by local physicians as being related to transfusion [
      • Inaba S.
      • Ito A.
      • Miyata Y.
      • Ishii H.
      • Kajimoto S.
      • Tanaka M.
      • et al.
      Individual nucleic amplification technology does not prevent all hepatitis B virus transmission by blood transfusion.
      ]. Twenty UK cases of hepatitis B associated with presumably infectious donors were identified (but only four were confirmed) over the past 15 years, none of which were suspected by local physicians in a timely fashion [
      • Soldan K.
      • Barbara J.A.J.
      • Dow B.C.
      Transfusion-transmitted hepatitis B virus infection in the UK: a small and moving target.
      ]. Clinical data suggest that only 20–35% of recipients will be symptomatic, and the length of the incubation period before symptoms develop can extend up to 6 months, irrespective of the amount of virus transfused [
      • Hollinger F.B.
      Hepatitis B virus infection and transfusion medicine: science and the occult.
      ,
      • Matsumoto C.
      • Tadokoro K.
      • Fujimura K.
      • Hirakawa S.
      • Mitsunaga S.
      • Juji T.
      Analysis of HBV infection after blood transfusion in Japan through investigation of a comprehensive donor specimen repository.
      ]. HBV incubation time can be considerably prolonged (up to 13 months) in unusual circumstances involving an impaired immune system and active or passive neutralizing antibodies to HBV in the recipient [
      • Wendel S.
      • Levi J.E.
      • Biagini S.
      • Candotti D.
      • Allain J.-P.
      A probable case of hepatitis B virus transfusion transmission revealed after a 13-month-long window period.
      ,
      • Gerlich W.H.
      • Wagner F.F.
      • Chudy M.
      • Holm Harritshoj L.
      • Lattermann A.
      • Wienzek S.
      • et al.
      HBsAg non-reactive HBV infection in blood donors: transmission and pathogenicity.
      ]. There is preliminary evidence that immunocompromised patients are not only more susceptible to lower infectious dose including in the presence of anti-HBs but also at higher risk of developing chronic infection [
      • Roche B.
      • Feray C.
      • Gigou M.
      • Roque-Afonso A.M.
      • Arulnaden J.L.
      • Delvart V.
      • et al.
      HBV DNA persistence 10 years after liver transplantation despite successful anti-HBs passive immunoprophylaxis.
      ]. The ∼50% mortality rate within 6–12 months post-transfusion reported in transfusion recipients may also limit identification of HBV transmission [
      • Hollinger F.B.
      • Dodd R.Y.
      Hepatitis B virus traceback and lookback: factors to consider.
      ].
      Lookback of recipients who were transfused with donations from a newly identified HBV-infected repeat donor is often used to identify recipients at risk of HBV transfusion transmission [
      • Hollinger F.B.
      • Dodd R.Y.
      Hepatitis B virus traceback and lookback: factors to consider.
      ]. Evidence of transfusion transmission of HBV may not be obtained because pre-transfusion samples are rarely available, HBV infections might have resolved before they are identified by lookback, and often recipients cannot be traced or samples obtained [
      • O’Brien S.
      • Yi Q.-L.
      • Fan W.
      • Scalia V.
      • Kleinman S.H.
      • Vamvakas E.C.
      Current incidence and estimated residual risk of transfusion-transmitted infections in donations made to Canadian Blood Services.
      ]. As HBV marker levels may fluctuate over time [
      • Kuhns M.C.
      • Kleinman S.H.
      • McNamara A.L.
      • Rawal B.
      • Glynn S.
      • Busch M.P.
      Lack of correlation between HBsAg and HBV DNA levels in blood donors who test positive for HBsAg and anti-HBc: implications for future HBV screening policy.
      ,
      • Inaba S.
      • Ito A.
      • Miyata Y.
      • Ishii H.
      • Kajimoto S.
      • Tanaka M.
      • et al.
      Individual nucleic amplification technology does not prevent all hepatitis B virus transmission by blood transfusion.
      ], follow-up of suspected donors and testing of archived samples are necessary to exclude recent infection and false-positive [
      • Grob P.
      • Jilg W.
      • Bornhak H.
      • Gerken G.
      • Gerlich W.
      • Günther S.
      • et al.
      Serological pattern “anti-HBc alone”: report on a workshop.
      ,
      • Allain J.P.
      • Hewitt P.E.
      • Tedder R.S.
      • Williamson L.
      Evidence that anti-HBc but not HBV DNA testing may prevent some HBV transmission by transfusion.
      ,
      • Allain J.P.
      • Belkhiri D.
      • Vermeulen M.
      • Crookes R.
      • Cable R.
      • Amiri A.
      • et al.
      Characterization of occult hepatitis B virus strains in South African blood donors.
      ]. Testing for archived donations and recipient samples requires access to a frozen repository of donor/recipient samples. Such system exists in several national blood services [
      • Matsumoto C.
      • Tadokoro K.
      • Fujimura K.
      • Hirakawa S.
      • Mitsunaga S.
      • Juji T.
      Analysis of HBV infection after blood transfusion in Japan through investigation of a comprehensive donor specimen repository.
      ,
      • Satake M.
      • Taira R.
      • Yugi H.
      • Hino S.
      • Kanemitsu K.
      • Ikeda H.
      • et al.
      Infectivity of blood components with low hepatitis B virus DNA levels identified in a lookback program.
      ,
      • Franklin I.M.
      • Dow B.C.
      • Jordan A.D.
      Benefits of a blood donation archive repository: international survey of donor repository procedures and Scottish experiences.
      ].
      Post-transfusion hepatitis B is not necessarily transfusion-transmitted and iatrogenic sources of infection should be systematically investigated before concluding that HBV-infected blood donors are involved in viral transmission [
      • Liu C.J.
      • Lo S.H.
      • Kao J.H.
      • Tseng P.T.
      • Lai M.Y.
      • Ni Y.H.
      • et al.
      Transmission of occult hepatitis B virus by transfusion to adult and pediatric recipients in Taiwan.
      ,
      • Allain J.P.
      Occult hepatitis B virus infection and transfusion.
      ,
      • Prati D.
      • Gerosa A.
      • Porretti L.
      Occult HBV infection and blood transfusion.
      ]. In a systematic investigation of suspected transfusion-transmitted HBV infections, Matsumoto and colleagues showed that the majority of reported cases could not be linked to laboratory testing of transfused blood [
      • Matsumoto C.
      • Tadokoro K.
      • Fujimura K.
      • Hirakawa S.
      • Mitsunaga S.
      • Juji T.
      Analysis of HBV infection after blood transfusion in Japan through investigation of a comprehensive donor specimen repository.
      ]. Caution should be exercised in concluding that a suspected transfusion-transmitted case is causally related to transfusion, unless other iatrogenic sources of infection have been eliminated, adequate donor follow-up and laboratory testing have been performed, and more importantly, pre- and post-transfusion testing of recipients has been completed. Unfortunately, pre-transfusion testing of the recipient is missing in many studies making difficult to establish if the investigated recipient was infected before or after transfusion [
      • O’Brien S.
      • Yi Q.-L.
      • Fan W.
      • Scalia V.
      • Kleinman S.H.
      • Vamvakas E.C.
      Current incidence and estimated residual risk of transfusion-transmitted infections in donations made to Canadian Blood Services.
      ,
      • Gerlich W.H.
      • Wagner F.F.
      • Chudy M.
      • Holm Harritshoj L.
      • Lattermann A.
      • Wienzek S.
      • et al.
      HBsAg non-reactive HBV infection in blood donors: transmission and pathogenicity.
      ,
      • Liu C.J.
      • Lo S.H.
      • Kao J.H.
      • Tseng P.T.
      • Lai M.Y.
      • Ni Y.H.
      • et al.
      Transmission of occult hepatitis B virus by transfusion to adult and pediatric recipients in Taiwan.
      ]. In addition, HBV reactivation has been largely documented in immunocompromised individuals with past history of hepatitis [123 for review]. Dependent on the degree of T-cell depletion, the risk of reactivation varies, low as demonstrated in kidney transplant recipients, or high in liver transplant recipients or patients treated for graft-versus-host disease or undergoing allogeneic bone marrow or stem cell transplantation or treatment with aggressive chemotherapy or monoclonal antibodies against T- or B-cells. In the latter groups, close monitoring of HBV DNA for anti-HBc-positive recipients or systematic treatment with antiviral drugs (i.e. lamivudine) have been advocated [
      • Liang R.
      How I treat and monitor viral hepatitis B infection in patients receiving intensive immunosuppressive therapies or undergoing hematopoietic stem cell transplantation.
      ]. Definitive evidence of transfusion transmission can be obtained by genomic analysis of the viral strains present in both donor and recipient.

      5. Conclusions

      Despite continuous technical improvement in blood donation screening, hepatitis B infection remains a major risk of transfusion-transmitted viral infection. The residual risk of HBV transmission is related to the pre-seroconversion window period, infection with immunovariant viruses, and with occult carriage of HBV. Reduction of HBV residual risk is achieved by developing more sensitive HBsAg tests, by adopting anti-HBc screening if appropriate, and recently by implementing HBV nucleic acid testing, either in minipools or more efficiently in individual samples. Compared to serological testing, HBV NAT combines the ability to significantly reduce the window period and to detect occult HBV carriage. HBV NAT yield in HBsAg-negative blood donations was studied in low-, moderate-, and high-endemic areas in pools and individual plasmas. Anti-HBc screening has the potential of excluding the majority of OBIs, leaving only the rare cases of primary OBI or of escape mutant associated with anti-HBs alone. However, it does not detect pre-seroconversion window period infections, and is not practical in areas with anti-HBc prevalence >5% where too many donor deferrals would negatively impact the blood supply. Based on available data, NAT is the only theoretical choice to reduce HBV risk in high-endemic countries. However, most of these countries do not have access to and could not afford such technology. Alternatives to simplify methods and to reduce NAT cost should be investigated.
      The development of HBV NAT assays substantiated decades of clinical observation that HBsAg-negative/anti-HBc-positive blood could transmit HBV. For the transfusion community, the remaining critical question is: are blood components from OBI donations infectious by transfusion? Clinical observations suggest limited transmission rate compared to WP yield cases. Low transmission rate may be related to the low viral loads generally observed in OBIs (even if the HBV infectious dose by transfusion is still unknown) or to the presence of defective variants associated with occult carriage. OBIs carrying detectable anti-HBs (∼50%) are essentially not infectious by transfusion. However, recent data suggest that the neutralizing capacity of low anti-HBs may be inefficient when overcome by exposure to high viral load. Anti-HBc blood units without detectable anti-HBs appear moderately infectious except in immunocompromised recipients. Immunodeficient elderly and patients receiving immunosuppressive treatments (organ transplantation or cancer chemotherapy) may be susceptible to infection with lower infectious dose even in the presence of anti-HBs. The immune status of blood recipients should be taken into consideration when investigating “post-transfusion” HBV infection. Pre-transfusion testing and post-transfusion long-term follow-up of recipients, and molecular analysis of the virus infecting both donor and recipient appear essential to definitively confirm transfusion transmission of HBV.

      References

        • Shepard C.W.
        • Simard E.P.
        • Finelli L.
        • Fiore A.E.
        • Bell B.P.
        Hepatitis B virus infection: epidemiology and vaccination.
        Epidemiol Rev. 2006; 28: 112-125
        • Allain J.P.
        Occult hepatitis B virus infection: implications in transfusion.
        Vox Sang. 2004; 86: 83-91
        • Hollinger F.B.
        Hepatitis B virus infection and transfusion medicine: science and the occult.
        Transfusion. 2008; 48: 1001-1026
        • Biswas R.
        • Tabor E.
        • Hsia C.C.
        • Wright D.J.
        • Laycock M.E.
        • Fiebig E.W.
        • et al.
        Comparative sensitivity of HBV NATs and HBsAg assays for detection of acute HBV infection.
        Transfusion. 2003; 43: 788-798
        • Scheiblauer H.
        • Soboll H.
        • Nick S.
        Evaluation of 17 CE-marked HBsAg assays with respect to clinical sensitivity, analytical sensitivity, and hepatitis B virus mutant detection.
        J Med Virol. 2006; 78: S66-S70
        • Matsubara N.
        • Kusano O.
        • Sugamata Y.
        • Itoh T.
        • Mizuii M.
        • Tanaka J.
        • et al.
        A novel hepatitis B virus surface antigen immunoassay as sensitive as hepatitis B virus nucleic acid testing in detecting early infection.
        Transfusion. 2009; 45: 585-595
        • Lien T.X.
        • Tien N.T.
        • Chanpong G.F.
        • Cuc C.T.
        • Yen V.T.
        • Soderquist R.
        • et al.
        Evaluation of rapid diagnostic tests for the detection of human immunodeficiency virus types 1 and 2, hepatitis B surface antigen, and syphilis in Ho Chi Minh City, Vietnam.
        Am J Trop Med Hyg. 2000; 62: 301-309
        • Owusu-Ofori S.
        • Temple J.
        • Sarkodie F.
        • Anokwa M.
        • Candotti D.
        • Allain J.P.
        Predonation screening of blood donors with rapid tests: implementation and efficacy of a novel approach to blood safety in resource-poor settings.
        Transfusion. 2005; 45: 133-140
        • Randrianirina F.
        • Carod J.F.
        • Ratsima E.
        • Chrétien J.B.
        • Richard V.
        • Talarmin A.
        Evaluation of the performance of four rapid tests for detection of hepatitis B surface antigen in Antananarivo, Madagascar.
        J Virol Methods. 2008; 151: 294-297
        • Allain J.P.
        • Candotti D.
        • Soldan K.
        • Sarkodie F.
        • Phelps B.
        • Giachetti C.
        • et al.
        The risk of hepatitis B virus infection by transfusion in Kumasi, Ghana.
        Blood. 2003; 101: 2419-2425
        • Weber B.
        • Dengler T.
        • Berger A.
        • Doerr H.W.
        • Rabenau H.
        Evaluation of two new automated assays for hepatitis B virus surface antigen (HBsAg) detection: IMMULITE HBsAg and IMMULITE 2000 HBsAg.
        J Clin Microbiol. 2003; 41: 135-143
        • Olinger C.M.
        • Weber B.
        • Otegbayo J.A.
        • Ammerlaan W.
        • van der Taelem-Brulé N.
        • Muller C.P.
        Hepatitis B virus genotype E surface antigen detection with different immunoassays and diagnostic impact of mutations in the preS/S gene.
        Med Microbiol Immunol. 2007; 196: 247-252
        • Weber B.
        Genetic variability of the S gene of hepatitis B virus: clinical and diagnostic impact.
        J Clin Virol. 2005; 32: 102-112
        • Hsu H.-Y.
        • Chang M.-H.
        • Ni Y.-H.
        • Chen H.-L.
        Survey of hepatitis B surface variant infection in children 15 years after a nationwide vaccination programme in Taiwan.
        Gut. 2004; 53: 1499-1503
        • Theamboonlers A.
        • Chongsrisawat V.
        • Jantaradsamee P.
        • Poovorawan Y.
        Variants within the “a” determinant of HBs gene in children and adolescents with and without hepatitis B vaccination as part of Thailand’s Expanded Program on Immunization (EPI).
        Tohoku J Exp Med. 2001; 193: 197-205
        • Joller-Jemelka H.I.
        • Wicki A.N.
        • Grob P.J.
        Detection of HBs antigen in “anti-HBc alone” positive sera.
        J Hepatol. 1994; 21: 269-272
        • Zhang J.M.
        • Xu Y.
        • Wang X.Y.
        • Yin Y.K.
        • Wu X.H.
        • Weng X.H.
        • et al.
        Coexistence of hepatitis B surface antigen (HBsAg) and heterologous subtype-specific antibodies to HBsAg among patients with chronic hepatitis B virus infection.
        Clin Infect Dis. 2007; 44: 1161-1169
        • Kiely P.
        • Stewart Y.
        • Castro L.
        Analysis of voluntary blood donors with biologic false reactivity on chemiluminescent immunoassays and implications for donor management.
        Transfusion. 2003; 43: 584-590
      1. Vermeulen M, Lelie N, Sykes W, Crookes R, Swanevelder J, Gaggia L, et al. Impact of individual-donation nucleic acid testing on risk of human immunodeficiency virus, hepatitis B virus, and hepatitis C virus transmission by blood transfusion in South Africa. Transfusion 2009 Feb 27. [Epub ahead of print].

        • Dow B.C.
        • Yates P.
        • Galea G.
        • Munro H.
        • Buchanan I.
        • Ferguson K.
        Hepatitis B vaccines may be mistaken for confirmed hepatitis B surface antigen-positive blood donors.
        Vox Sang. 2002; 82: 15-17
        • Davis A.R.
        • Brotchie H.L.
        • Mundkur B.A.
        • Ismary S.L.
        Transient hepatitis B surface antigenemia in a blood donor after a combination hepatitis A and B vaccine.
        Transfusion. 2003; 43: 545
        • Roth W.K.
        • Seifried E.
        The German experience with NAT.
        Trans Med. 2002; 12: 255-258
        • Kleinman S.H.
        • Kuhns M.C.
        • Todd D.S.
        • Glynn S.A.
        • McNamara A.
        • DiMarco A.
        • et al.
        Frequency of HBV DNA detection in US blood donors testing positive for the presence of anti-HBc: implications for transfusion transmission and donor screening.
        Transfusion. 2003; 43: 696-704
        • Schifman R.B.
        • Rivers S.L.
        • Sampliner R.E.
        • Krammes J.E.
        Significance of isolated hepatitis B core antibody in blood donors.
        Arch Intern Med. 1993; 153: 2261-2266
        • Almeida Neto C.
        • Strauss E.
        • Sabino E.C.
        • Sucupira M.C.
        • Chamone D.A.
        Significance of isolated hepatitis B core antibody in blood donors from São Paulo.
        Rev Inst Med Trop Sao Paulo. 2001; 43: 203-208
        • Brojer E.
        • Grabarczyk P.
        • Liszewski G.
        • Mikulska M.
        • Allain J.P.
        • Letowska M.
        • et al.
        Characterization of HBV DNA+/HBsAg− blood donors in Poland identified by triplex NAT.
        Hepatology. 2006; 44: 1666-1674
        • Velati C.
        • Romano L.
        • Fomiatti L.
        • Baruffi L.
        • Zanetti A.R.
        • SIMTI Research Group
        Impact of nucleic acid testing for hepatitis B virus, hepatitis C virus, and human immunodeficiency virus on the safety of blood supply in Italy: a 6-year survey.
        Transfusion. 2008; 48: 2205-2213
        • Margaritis A.R.
        • Brown S.M.
        • Seed C.R.
        • Kiely P.
        • D’Agostino B.
        • Keller A.J.
        Comparison of two automated nucleic acid testing systems for simultaneous detection of human immunodeficiency virus and hepatitis C virus RNA and hepatitis B virus DNA.
        Transfusion. 2007; 47: 1783-1793
        • Nantachit N.
        • Thaikruea L.
        • Thongsawat S.
        • Leetrakool N.
        • Fongsatikul L.
        • Sompan P.
        • et al.
        Evaluation of a multiplex human immunodeficiency virus-1, hepatitis C virus, and hepatitis B virus nucleic acid testing assay to detect viremic blood donors in northern Thailand.
        Transfusion. 2007; 47: 1803-1808
        • Li L.
        • Chen P.J.
        • Chen M.H.
        • Chak K.F.
        • Lin K.S.
        • Lin Tsai S.J.
        A pilot study for screening blood donors in Taiwan by nucleic acid amplification technology: detecting occult hepatitis B virus infections and closing the serologic window period for hepatitis C virus.
        Transfusion. 2008; 48: 1198-1206
        • Matsumoto C.
        • Tadokoro K.
        • Fujimura K.
        • Hirakawa S.
        • Mitsunaga S.
        • Juji T.
        Analysis of HBV infection after blood transfusion in Japan through investigation of a comprehensive donor specimen repository.
        Transfusion. 2001; 41: 878-884
        • Sato S.
        • Ohhashi W.
        • Ihara H.
        • Sakaya S.
        • Kato T.
        • Ikeda H.
        Comparison of the sensitivity of NAT using pooled donor samples for HBV and that of a serologic HBsAg assay.
        Transfusion. 2001; 41: 1107-1113
        • Yotsuyanagi H.
        • Yasuda K.
        • Moriya K.
        • Shintani Y.
        • Fujie H.
        • Tsutsumi T.
        • et al.
        Frequent presence of HBV in the sera of HBsAg-negative, anti-HBc-positive blood donors.
        Transfusion. 2001; 41: 1093-1099
        • Koppelman M.H.G.
        • Sjerps M.C.
        • Reesink H.W.
        • Cuypers H.T.M.
        Evaluation of COBAS AmpliPrep nucleic acid extraction in conjunction with COBAS AmpliScreen HBV DNA, HCV RNA and HIV-1 RNA amplification and detection.
        Vox Sang. 2005; 89: 193-200
        • Raimondo G.
        • Allain J.P.
        • Brunetto M.R.
        • Buendia M.A.
        • Chen D.S.
        • Colombo M.
        • et al.
        Statements from the Taormina expert meeting on occult hepatitis B virus infection.
        J Hepatol. 2008; 49: 654-659
        • Candotti D.
        • Grabarczyk P.
        • Ghiazza P.
        • Roig R.
        • Casamitjana N.
        • Iudicone P.
        • et al.
        Characterization of occult hepatitis B virus from blood donors carrying genotype A2 or genotype D strains.
        J Hepatol. 2008; 49: 537-547
        • Marusawa H.
        • Uemoto S.
        • Hijikata M.
        • Ueda Y.
        • Tanaka K.
        • Shimotohno K.
        • et al.
        Latent hepatitis B virus infection in healthy individuals with antibodies to hepatitis B core antigen.
        Hepatology. 2000; 31: 488-495
        • Hass M.
        • Hannoun C.
        • Kalinina T.
        • Sommer G.
        • Manegold C.
        • Gunther S.
        Functional analysis of hepatitis B virus reactivating in hepatitis B surface antigen-negative individuals.
        Hepatology. 2005; 42: 93-103
        • Baginski I.
        • Chemin I.
        • Hantz O.
        • Pichoud C.
        • Jullien A.M.
        • Chevre J.C.
        • et al.
        Transmission of serologically silent hepatitis B virus along with hepatitis C virus in two cases of posttransfusion hepatitis.
        Transfusion. 1992; 32: 215-220
        • Manzini P.
        • Abate M.L.
        • Valpreda C.
        • Milanesi P.
        • Curti F.
        • Rizzetto M.
        • et al.
        Evidence of acute primary occult hepatitis B virus infection in an Italian repeat blood donor.
        Transfusion. 2009; 49: 757-764
        • Yoshikawa A.
        • Gotanda Y.
        • Minegishi K.
        • Taira R.
        • Hino S.
        • Tadokoro K.
        • et al.
        Lengths of hepatitis B viremia and antigenemia in blood donors: preliminary evidence of occult (hepatitis B surface antigen-negative) infection in the acute stage.
        Transfusion. 2007; 47: 1162-1171
        • Dow B.C.
        • Peterkin M.A.
        • Green R.H.A.
        • Cameron S.O.
        Hepatitis B virus transmission by blood donation negative for hepatitis B surface antigen, antibody to HBsAg, antibody to hepatitis B core antigen and HBV DNA.
        Vox Sang. 2001; 81: 140
        • Busch M.P.
        Should HBV DNA NAT replace HBsAg and/or anti-HBc screening of blood donors?.
        Trans Clin Biol. 2004; 11: 26-32
        • Yugi H.
        • Mizui M.
        • Tanaka J.
        • Yoshizawa H.
        Hepatitis B virus (HBV) screening strategy to ensure the safety of blood for transfusion through a combination of immunological testing and nucleic acid amplification testing – Japanese experience.
        J Clin Virol. 2006; 36: S56-S64
        • Jackson B.R.
        • Busch M.P.
        • Stramer S.L.
        • AuBuchon J.P.
        The cost-effectiveness of NAT for HIV, HCV, and HBV in whole-blood donations.
        Transfusion. 2003; 43: 721-729
        • Busch M.
        • Walderhaug M.
        • Custer B.
        • Allain J.P.
        • Reddy R.
        • McDonough B.
        Risk assessment and cost-effectiveness/utility analysis.
        Biologicals. 2009; 37: 78-87
        • Kuhns M.C.
        • Kleinman S.H.
        • McNamara A.L.
        • Rawal B.
        • Glynn S.
        • Busch M.P.
        Lack of correlation between HBsAg and HBV DNA levels in blood donors who test positive for HBsAg and anti-HBc: implications for future HBV screening policy.
        Transfusion. 2004; 44: 1332-1339
        • Nardone A.
        • Anastassopoulou C.G.
        • Theeten H.
        • Kriz B.
        • Davidkin I.
        • Thierfelder W.
        • et al.
        A comparison of hepatitis B seroepidemiology in ten European countries.
        Epidemiol Infect. 2008; 23: 1-9
        • Ni Y.H.
        • Huang L.M.
        • Chang M.H.
        • Yen C.J.
        • Lu C.Y.
        • You S.L.
        • et al.
        Two decades of universal hepatitis B vaccination in Taiwan: impact and implication for future strategies.
        Gastroenterology. 2007; 132: 1287-1293
        • Chang M.W.
        Impact of hepatitis B vaccination on hepatitis B disease and nucleic acid testing in high-prevalence populations.
        J Clin Virol. 2006; 36: S45-S50
        • Pereira J.S.F.
        • Goncales N.S.L.
        • Silva C.
        • Lazarini M.S.K.
        • Pavan M.H.P.
        • Fais V.C.
        • et al.
        HBV vaccination of HCV-infected patients with occult HBV infection and anti-HBc-positive blood donors.
        Braz J Med Biol Res. 2006; 39: 525-531
        • Singh H.
        • Pradhan M.
        • Singh R.L.
        • Phadke S.
        • Naik S.R.
        • Aggarwal R.
        • et al.
        High frequency of hepatitis B virus infection in patients with β-thalassemia receiving multiple transfusions.
        Vox Sang. 2003; 84: 292-299
        • Coste J.
        • Reesink H.W.
        • Engelfriet C.P.
        • Laperche S.
        • Brown S.
        • Busch M.P.
        • et al.
        Implementation of donor screening for infectious agents transmitted by blood by nucleic acid technology: update to 2003.
        Vox Sang. 2005; 88: 289-303
        • Kleinman S.H.
        • Busch M.P.
        Assessing the impact of HBV NAT on window period reduction and residual risk.
        J Clin Virol. 2006; 36: S23-S29
        • Busch M.P.
        • Glynn S.A.
        • Stramer S.L.
        • Strong D.M.
        • Caglioti S.
        • Wright D.J.
        • et al.
        A new strategy for estimating risks of transfusion-transmitted viral infections based on rates of detection of recently infected donors.
        Transfusion. 2005; 45: 254-264
        • Van der Bij A.K.
        • Coutinho R.A.
        • van der Poel C.L.
        Surveillance of risk profiles among new and repeat blood donors with transfusion-transmissible infections from 1995 through 2003 in the Netherlands.
        Transfusion. 2006; 46: 1729-1736
        • Korelitz J.J.
        • Busch M.P.
        • Kleinman S.H.
        • Williams A.E.
        • Gilcher R.O.
        • Ownby H.E.
        • et al.
        A method for estimating hepatitis B virus incidence rates in volunteer blood donors. National Heart, Lung, and Blood Institute Retrovirus Epidemiology Donor Study.
        Transfusion. 1997; 37: 634-640
        • Janssen M.P.
        • Cator E.A.
        • van der Poel C.L.
        • Schaasberg W.P.
        • Bonsel G.J.
        • van Hout B.A.
        Monitoring viral incidence rates: tools for the implementation of European Union regulations.
        Vox Sang. 2009; 96: 298-308
        • Soldan K.
        • Davison K.
        • Dow B.
        Estimates of the frequency of HBV, HCV, and HIV infectious donations entering the blood supply in the United Kingdom, 1996 to 2003..
        Euro Surveill. 2005; 10: 17-19
        • Laperche S.
        • Maniez M.
        • Barlet V.
        • El Ghouzzi M.-H.
        • Le Vacon F.
        • Levayer T.
        • et al.
        A revised method for estimating hepatitis B virus transfusion residual risk based on antibody to hepatitis B core antigen incident cases.
        Transfusion. 2008; 48: 2308-2314
        • Offergeld R.
        • Faensen D.
        • Ritter S.
        • Hamouda O.
        Human immunodeficiency virus, hepatitis C and hepatitis B infections among blood donors in Germany 2000–2002: risk of virus transmission and the impact of nucleic acid amplification testing.
        Euro Surveill. 2005; 10: 8-11
        • Niederhauser C.
        • Schneider P.
        • Fopp M.
        • Ruefer A.
        • Levy G.
        Incidence of viral markers and evaluation of the estimated risk in the Swiss blood donor population from 1996 to 2003.
        Euro Surveill. 2005; 10: 14-16
        • O’Brien S.
        • Yi Q.-L.
        • Fan W.
        • Scalia V.
        • Kleinman S.H.
        • Vamvakas E.C.
        Current incidence and estimated residual risk of transfusion-transmitted infections in donations made to Canadian Blood Services.
        Transfusion. 2007; 47: 316-325
        • Dodd R.Y.
        • Notari 4th, E.P.
        • Stramer S.L.
        Current prevalence and incidence of infectious disease markers and estimated window-period risk in the American Red Cross blood donor population.
        Transfusion. 2002; 42: 975-979
        • Kleinman S.H.
        • Strong D.M.
        • Tegtmeier G.G.E.
        • Holland P.V.
        • Gorlin J.B.
        • Cousins C.R.
        • et al.
        Hepatitis B virus (HBV) DNA screening of blood donations in minipools with the COBAS AmpliScreen HBV test.
        Transfusion. 2005; 45: 1247-1257
        • Seed C.R.
        • Kiely P.
        • Keller A.J.
        Residual risk of transfusion transmitted human immunodeficiency virus, hepatitis B virus, hepatitis C virus and human T lymphotrophic virus.
        Intern Med J. 2005; 35: 592-598
        • Tosti M.E.
        • Solinas S.
        • Prati D.
        • Salvaneschi L.
        • Manca M.
        • Francesconi M.
        • et al.
        An estimate of the current risk of transmitting blood–borne infections through blood transfusion in Italy.
        Br J Haematol. 2002; 117: 215-219
        • Alvarez do Barrio M.
        • Gonzalez Diez R.
        • Hernandez Sanchez J.M.
        • Oyonarte Gomez S.
        Residual risk of transfusion-transmitted viral infections in Spain, 1997–2002, and impact of nucleic acid testing.
        Euro Surveill. 2005; 10: 20-22
        • Shang G.
        • Seed C.R.
        • Wang F.
        • Nie D.
        • Farrugia A.
        Residual risk of transfusion-transmitted viral infections in Shenzhen, China, 2001 through 2004.
        Transfusion. 2007; 47: 529-539
        • Allain J.P.
        Estimation of HBV transfusion risk.
        Transfusion. 2009; 49: 1019-1021
        • Schmidt M.
        • Nubling C.M.
        • Scheiblauer H.
        • Chudy M.
        • Walch L.A.
        • Seifried E.
        • et al.
        Anti-HBc screening of blood donors: a comparison of nine anti-HBc tests.
        Vox Sang. 2006; 91: 237-243
        • Hennig H.
        • Puchta I.
        • Luhm J.
        • Schlenke P.
        • Goerg S.
        • Kirchner H.
        Frequency and load of hepatitis B virus DNA in first-time blood donors with antibodies to hepatitis B core antigen.
        Blood. 2002; 100: 2637-2641
        • Vitale F.
        • Tramuto F.
        • Orlando A.
        • Vizzini G.
        • Meli V.
        • Cerame G.
        • et al.
        Can the serological status of anti-HBc alone be considered a sentinel marker for detection of occult HBV infection?.
        J Med Virol. 2008; 80: 577-582
        • Chevrier M.C.
        • St-Louis M.
        • Perreault J.
        • Caron B.
        • Castilloux C.
        • Laroche J.
        • et al.
        Detection and characterization of hepatitis B virus of anti-hepatitis B core antigen-reactive blood donors in Quebec with an in-house nucleic acid testing assay.
        Transfusion. 2007; 47: 1794-1802
        • O’Brien S.F.
        • Fearon M.A.
        • Yi Q.-L.
        • Fan W.
        • Scalia V.
        • Muntz I.R.
        • et al.
        Hepatitis B virus DNA-positive, hepatitis B surface antigen-negative blood donations intercepted by anti-hepatitis B core antigen testing: the Canadian Blood Services experience.
        Transfusion. 2007; 47: 1809-1815
        • Hourfar M.K.
        • Jork C.
        • Schottstedt V.
        • Weber-Schehl M.
        • Brixner V.
        • Busch M.P.
        • et al.
        Experience of German red cross blood donor services with nucleic acid testing: results of screening more than 30 million blood donations for human immunodeficiency virus-1, hepatitis C virus, and hepatitis B virus.
        Transfusion. 2008; 48: 1558-1566
        • Stramer S.L.
        Current risks of transfusion-transmitted agents.
        Arch Pathol Lab Med. 2007; 131: 702-707
        • Ramia S.
        • Ramlawi F.
        • Kanaan M.
        • Klayme S.
        • Naman R.
        Frequency and significance of antibodies against hepatitis B core (anti-HBc) antigen as the only serological marker for hepatitis B infection in Lebanese blood donors.
        Epidemiol Infect. 2005; 133: 695-699
        • Katsoulidou A.
        • Moschidis Z.
        • Sypsa V.
        • Chini M.
        • Papatheodoridis G.V.
        • Tassopoulos N.C.
        • et al.
        Analytical and clinical sensitivity of the Procleix Ultrio HIV-1/HCV/HBV assay in samples with a low viral load.
        Vox Sang. 2007; 92: 8-14
        • Manzini P.
        • Girotto M.
        • Borsotti R.
        • Giachino O.
        • Guaschino R.
        • Lanteri M.
        • et al.
        Italian blood donors with anti-HBc and occult hepatitis B virus infection.
        Haematologica. 2007; 92: 1664-1670
        • Makroo R.N.
        • Choudhury N.
        • Jagannathan L.
        • Parihar-Malhotra M.
        • Raina V.
        • Chaudhary R.K.
        • et al.
        Multicenter evaluation of individual donor nucleic acid testing (NAT) for simultaneous detection of human immunodeficiency virus-1 & hepatitis B & C viruses in Indian blood donors.
        Indian J Med Res. 2008; 127: 140-147
        • Comanor L.
        • Holland P.
        Hepatitis B virus blood screening: unfinished agendas.
        Vox Sang. 2006; 91: 1-12
        • Liu C.J.
        • Chen D.S.
        • Chen P.J.
        Epidemiology of HBV infection in Asian blood donors: emphasis on occult HBV infection and the role of NAT.
        J Clin Virol. 2006; 36: S33-S44
        • Komiya Y.
        • Katayama K.
        • Yugi H.
        • Mizui M.
        • Matsukura H.
        • Tomoguri T.
        • et al.
        Minimum infectious dose of hepatitis B virus in chimpanzees and difference in the dynamics of viremia between genotype A and genotype C.
        Transfusion. 2008; 48: 286-294
        • Hsia C.C.
        • Purcell R.H.
        • Farshid M.
        • Lachenbruch P.A.
        • Yu M.Y.
        Quantification of hepatitis B virus genomes and infectivity in human serum samples.
        Transfusion. 2006; 46: 1829-1835
        • Tsuge M.
        • Hiraga N.
        • Takaishi H.
        • Noguchi C.
        • Oga H.
        • Imamura M.
        • et al.
        Infection of human hepatocyte chimeric mouse with genetically engineered hepatitis B virus.
        Hepatology. 2005; 42: 1046-1054
        • Tabuchi A.
        • Tanaka J.
        • Katayama K.
        • Mizui M.
        • Matsukura H.
        • Yugi H.
        • et al.
        Titration of hepatitis B virus infectivity in the sera of pre-acute and late acute phases of HBV infection: transmission experiments to chimeric mice with human liver repopulated hepatocytes.
        J Med Virol. 2008; 80: 2064-2068
        • Inaba S.
        • Ito A.
        • Miyata Y.
        • Ishii H.
        • Kajimoto S.
        • Tanaka M.
        • et al.
        Individual nucleic amplification technology does not prevent all hepatitis B virus transmission by blood transfusion.
        Transfusion. 2006; 46: 2028-2029
        • Satake M.
        • Taira R.
        • Yugi H.
        • Hino S.
        • Kanemitsu K.
        • Ikeda H.
        • et al.
        Infectivity of blood components with low hepatitis B virus DNA levels identified in a lookback program.
        Transfusion. 2007; 47: 1197-1205
        • Wang J.T.
        • Lee C.Z.
        • Chen P.J.
        • Wang T.H.
        • Chen D.S.
        Transfusion-transmitted HBV infection in an endemic area: the necessity of more sensitive screening for HBV carriers.
        Transfusion. 2002; 42: 1592-1597
        • Hoofnagle J.H.
        • Waggoner J.G.
        Hepatitis A and B virus markers in immune serum globulin.
        Gastroenterology. 1980; 78: 259-263
        • Stramer S.L.
        Pooled hepatitis B virus DNA testing by nucleic acid amplification: implementation or not.
        Transfusion. 2005; 45: 1242-1246
        • Soldan K.
        • Barbara J.A.J.
        • Dow B.C.
        Transfusion-transmitted hepatitis B virus infection in the UK: a small and moving target.
        Vox Sang. 2002; 83: 305-308
        • Jongerius J.M.
        • van der Poel C.L.
        • van Leeuwen E.F.
        A simple strategy to look back on posttransfusion hepatitis B in a multitransfused patient.
        Vox Sang. 1998; 75: 66-69
        • Dreier J.
        • Kroger M.
        • Diekmann J.
        • Gotting C.
        • Kleesiek K.
        Low-level viraemia of hepatitis B virus in an anti-HBc- and anti-HBs-positive blood donor.
        Transfus Med. 2004; 14: 97-103
        • Gerlich W.H.
        Breakthrough of hepatitis B virus escape mutants after vaccination and virus reactivation.
        J Clin Virol. 2006; 36: S18-S22
        • Levicnik-Stezinar S.
        • Rahne-Potokar U.
        • Candotti D.
        • Lelie N.
        • Allain J.P.
        Anti-HBs positive occult hepatitis B virus carrier blood infectious in two transfusion recipients.
        J Hepatol. 2008; 48: 1022-1025
        • Wendel S.
        • Levi J.E.
        • Biagini S.
        • Candotti D.
        • Allain J.-P.
        A probable case of hepatitis B virus transfusion transmission revealed after a 13-month-long window period.
        Transfusion. 2008; 48: 1602-1608
        • Chudy M.
        • Schmidt M.
        • Czudai V.
        • Scheiblauer H.
        • Nick S.
        • Mosebach M.
        • et al.
        Hepatitis B virus genotype G monoinfection and its transmission by blood components.
        Hepatology. 2006; 44: 99-107
        • Gerlich W.H.
        • Wagner F.F.
        • Chudy M.
        • Holm Harritshoj L.
        • Lattermann A.
        • Wienzek S.
        • et al.
        HBsAg non-reactive HBV infection in blood donors: transmission and pathogenicity.
        J Med Virol. 2007; 79: S32-S36
        • Prince A.M.
        • Lee D.H.
        • Brotman B.
        Infectivity of blood from PCR-positive, HBsAg-negative, anti-HBs-positive cases of resolved hepatitis B infection.
        Transfusion. 2001; 41: 329-332
        • Barcena R.
        • Moraleda G.
        • Moreno J.
        • Martin M.D.
        • de Vicente E.
        • Nuno J.
        • et al.
        Prevention of de novo HBV infection by the presence of anti-HBs in transplanted patients receiving core antibody-positive livers.
        World J Gastroenterol. 2006; 12: 2070-2074
        • Dodson S.F.
        Prevention of de novo hepatitis B infection after liver transplantation with allografts from hepatitis B core antibody positive donors.
        Clin Transplant. 2000; 14: S20-S24
        • Roque-Afonso A.M.
        • Feray C.
        • Samuel D.
        • Simoneau D.
        • Roche B.
        • Emile J.F.
        • et al.
        Antibodies to hepatitis B surface antigen prevent viral reactivation in recipients of liver grafts from anti-HBc positive donors.
        Gut. 2002; 50: 95-99
        • Roche B.
        • Feray C.
        • Gigou M.
        • Roque-Afonso A.M.
        • Arulnaden J.L.
        • Delvart V.
        • et al.
        HBV DNA persistence 10 years after liver transplantation despite successful anti-HBs passive immunoprophylaxis.
        Hepatology. 2003; 38: 86-95
        • Grob P.
        • Jilg W.
        • Bornhak H.
        • Gerken G.
        • Gerlich W.
        • Günther S.
        • et al.
        Serological pattern “anti-HBc alone”: report on a workshop.
        J Med Virol. 2000; 62: 450-455
        • Allain J.P.
        • Hewitt P.E.
        • Tedder R.S.
        • Williamson L.
        Evidence that anti-HBc but not HBV DNA testing may prevent some HBV transmission by transfusion.
        Br J Haematol. 1999; 107: 186-195
        • Mosley J.W.
        • Stevens C.E.
        • Aach R.D.
        • Hollinger F.B.
        • Mimms L.T.
        • Solomon L.R.
        • et al.
        Donor screening for antibody to hepatitis B core antigen and hepatitis B virus infection in transfusion recipients.
        Transfusion. 1995; 35: 5-12
        • Liu C.J.
        • Lo S.H.
        • Kao J.H.
        • Tseng P.T.
        • Lai M.Y.
        • Ni Y.H.
        • et al.
        Transmission of occult hepatitis B virus by transfusion to adult and pediatric recipients in Taiwan.
        J Hepatol. 2006; 44: 39-46
        • Knoll A.
        • Boehm S.
        • Hahn J.
        • Holler E.
        • Jilg W.
        Long-term surveillance of haematopoietic stem cell recipients with resolved hepatitis B: high risk of viral reactivation even in a recipient with a vaccinated donor.
        J Viral Hepat. 2007; 14: 478-483
        • Su F.H.
        • Chen J.D.
        • Cheng S.H.
        • Sung K.Y.
        • Jeng J.J.
        • Chu F.Y.
        Waning-off effect of serum hepatitis B surface antibody amongst Taiwanese university students: 18 years post-implementation of Taiwan’s national hepatitis B vaccination programme.
        J Viral Hepat. 2008; 15: 14-19
        • Van Damme P.
        • Van Herck K.
        A review of the long-term protection after hepatitis A and B vaccination.
        Travel Med Infect Dis. 2007; 5: 79-84
        • Roche B.
        • Samuel D.
        • Gigou M.
        • Feray C.
        • Virot V.
        • Schmets L.
        • et al.
        De novo and apparent de novo hepatitis B virus infection after liver transplantation.
        J Hepatol. 1997; 26: 517-526
        • Dickson R.C.
        • Wright R.M.
        • Bacchetta M.D.
        • Bodily S.E.
        • Caldwell S.H.
        • Driscoll C.J.
        • et al.
        Quality of life of hepatitis B and C patients after liver transplantation.
        Clin Transplant. 1997; 11: 282-285
        • Uemoto S.
        • Sugiyama K.
        • Marusawa H.
        • Inomata Y.
        • Asonuma K.
        • Egawa H.
        • et al.
        Transmission of hepatitis B virus from hepatitis B core antibody-positive donors in living related liver transplants.
        Transplantation. 1998; 65: 494-499
        • Kim K.H.
        • Ahn S.H.
        • Chung H.Y.
        • Paik Y.H.
        • Lee K.S.
        • Kim Y.S.
        • et al.
        Hepatitis B virus infection after renal transplantation in the presence of antibody to hepatitis B surface antigen immunity.
        J Gastroenterol Hepatol. 2004; 19: 847-853
        • Llewelyn C.A.
        • Wells A.W.
        • Amin M.
        • Casbard A.
        • Johnson A.J.
        • Ballard S.
        • et al.
        The EASTR study: a new approach to determine the reasons for transfusion in epidemiological studies.
        Transfus Med. 2009; 19: 89-98
        • Hollinger F.B.
        • Dodd R.Y.
        Hepatitis B virus traceback and lookback: factors to consider.
        Transfusion. 2009; 49: 176-184
        • Allain J.P.
        • Belkhiri D.
        • Vermeulen M.
        • Crookes R.
        • Cable R.
        • Amiri A.
        • et al.
        Characterization of occult hepatitis B virus strains in South African blood donors.
        Hepatology. 2009; 49: 1868-1876
        • Franklin I.M.
        • Dow B.C.
        • Jordan A.D.
        Benefits of a blood donation archive repository: international survey of donor repository procedures and Scottish experiences.
        Transfusion. 2007; 47: 1172-1179
        • Allain J.P.
        Occult hepatitis B virus infection and transfusion.
        J Hepatol. 2006; 44: 618-619
        • Prati D.
        • Gerosa A.
        • Porretti L.
        Occult HBV infection and blood transfusion.
        J Hepatol. 2006; 44: 818
        • Liang R.
        How I treat and monitor viral hepatitis B infection in patients receiving intensive immunosuppressive therapies or undergoing hematopoietic stem cell transplantation.
        Blood. 2009; 113: 3147-3153