Refinement of a viral transmission risk model for blood donations in seroconversion window phase screened by nucleic acid testing in different pool sizes and repeat test algorithms

BACKGROUND: In minipool nucleic acid test (MP‐NAT) screening protocols, the donations implicated in reactive test pools are released for transfusion when they are nonreactive in a repeat test on the individual samples, but in individual‐donation (ID)‐NAT screening algorithms the release of nonrepeatable reactive (NRR) donations is under discussion. STUDY DESIGN AND METHODS: A previously developed window phase (WP) transmission risk model for NAT‐screened blood transfusions has been refined to take the effect of repeat tests of initially reactive (IR) MP‐ or ID‐NAT results into account. The model has then been applied to simulate the effect of different screening algorithms with ULTRIO and the new‐generation ULTRIO Plus assay (Novartis Diagnostics) on transmission risk for hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV). RESULTS: We calculated WP risk‐day equivalents for MP16‐, MP8‐, and ID‐NAT with and without duplicate retesting of IR results of 3.1, 2.7, 1.5, and 1.3 days for HCV; 6.3, 5.5, 3.3, and 2.9 days for HIV; and 24.4, 22.2, 15.6, and 14.1 days for HBV, respectively. These latter infectious HBV WPs reduced to 20.4, 18.2, 11.6, and 10.3 days, respectively, with the more sensitive ULTRIO Plus assay. CONCLUSION: ULTRIO Plus ID‐NAT screening reduces the virus transmission risk in the WP by 54% to 58% compared to ULTRIO MP16‐NAT, while the incremental risk caused by releasing donations with duplicate ID‐NAT NRR results is 5% to 6%. To achieve maximum safety and specificity a similar repeat test algorithm can be applied to ID‐NAT as used for serologic assays.     

Blood donation screening for hepatitis B virus markers in the era of nucleic acid testing: are all tests of value?

BACKGROUND: The American Red Cross implemented hepatitis B virus (HBV) minipool (MP)‐nucleic acid testing (NAT) in June 2009, in addition to existing tests for hepatitis B surface antigen (HBsAg) and antibodies to hepatitis B core antigen (anti‐HBc). The value of all three tests was evaluated. STUDY DESIGN AND METHODS: HBsAg, anti‐HBc, and HBV DNA (Ultrio MP‐NAT, Gen‐Probe/Novartis) donation results were analyzed during a 12‐month period (July 1, 2009‐June 30, 2010). Additional testing by individual‐donation (ID) polymerase chain reaction (PCR) to confirm donor infection was performed when any HBV screening test was reactive or positive, except in the case of HBsAg neutralization‐positive, anti‐HBc–reactive samples. Numbers of blood donations identified as reactive or positive versus nonreactive or negative were compared. RESULTS: Of about 6.5 million donations, 699 were defined as from HBV‐infected donors, of which 64% (444) were reactive for all three markers. More than 99% (697) had reactivity to one or both serologic tests with 68% (477) showing reactivity by MP‐NAT. Only two donations were DNA‐positive, seronegative NAT‐yield donations (1 per 3.23 million), fewer than expected (p = 0.0075). Among MP‐NAT–reactive donors, only small numbers represented early infection (2 or 0.4% with negative serology and 10 or 2.1% who were HBsAg confirmed positive, anti‐HBc nonreactive). Of the 142 occult HBV‐infected donors, 85% were MP‐NAT nonreactive requiring ID‐PCR for detection (121 or 54.5% of all MP‐NAT nonreactives vs. 21 or 4.4% of all MP‐NAT reactives). CONCLUSIONS: The HBV DNA–positive yield rate from MP‐NAT was lower than expected, likely representing the rarity of such findings even in very large studies. With the implementation of HBV MP‐NAT, the value of maintaining anti‐HBc for the detection of low‐level HBV DNA–positive donors was confirmed; however, HBsAg screening showed no blood safety value.     

单检及16份混样检测模式对献血者核酸检测效果的比较研究

目的 探讨单份及16份混合标本2种检测模式对献血者血液病毒核酸检测(nucleic acid test,NAT)效果的影响.方法 2009年2至6月顺序留取北京无偿献血者标本,用诺华Procleix ULTRIO Assay进行单份(ID)或16份混合标本(P16)乙型肝炎病毒(HBV)、丙型肝炎病毒(HCV)和人类免疫缺陷病毒-1( HIV-1)三项联合核酸检测.单份NAT反应性同时HBsAg、抗-HCV或抗-HIV血清学不合格的标本,血清学合格的单份NAT反应性经双孔NAT复检阳性的标本,以及混合NAT反应性/拆分NAT为阳性的标本,进一步用诺华Procleix HBV、HCV和HIV-1鉴别试剂进行鉴别试验.血清学合格、HBV NAT单独阳性标本进一步用Roche HBV定量实验加以验证和进行病毒含量测定、血清学分析、并进行稀释以模拟是否能被P16-NAT检出.阳性检出率进行四格表连续校正的x2检验.结果 (1)在7613份单份NAT (ID-NAT)标本中,检出NAT阳性26份,ID-NAT阳性率0.34％(26/7613);(2)在16 064份共1004份P16混合标本NAT(P16-NAT)中,检出NAT阳性27份,P16-NAT阳性率为0.17％ (27/16 064);(3)在血清学合格标本中,单份检测的NAT单独阳性检出率为0.12％ (9/7438),高于16份混样检测的NAT单独阳性检出率0.01％ (2/15 750)(x2=11.880,P＜0.05).9份ID-NAT及2份P16-NAT单独阳性标本经鉴别均为HBV NAT阳性,未检出 HCV NAT单独阳性或HIV NAT单独阳性;(4)9份ID-NAT HBV单独阳性血样模拟P16-NAT,仅有2份可被检出;(5)对8份ID-NAT及2份P16-NAT单独阳性标本进行Roche HBV定量测定,均可确证其核酸检测结果,但病毒含量很低.其中2份HBV病毒含量为472 IU/ml及15 IU/ml,6份含量＜12 IU/ml,另2份原倍不能定量经10倍浓缩处理后测得含量为＜ 12 IU/ml和14.3 IU/ml;(6)11份HBV NAT单独阳性标本中,3份(27.3％)为潜在的窗口期感染,其余8份(72.7％)抗-HBc阳性或抗-HBe阳性,但抗-HBc-IgM均为阴性,为隐匿性感染;(7) P16-NAT初检呈反应性需要进行拆分试验的混合样本比率为2.49％ (25/1004),其中由血清学合格标本所致初检反应性的混合样本比率为0.20％ (2/1004).结论 ID-NAT单独阳性检出率高于P16-NAT单独阳性检出率.为避免低病毒含量HBV的漏检,应选用灵敏度高的核酸检测试剂,并尽量采用小标本量混合检测,甚至采用单份检测方式.     

Trends in prevalence,incidence, and residual risk of major transfusion‐transmissible viral infections in United Arab Emirates blood donors: impact of individual‐donation nucleic acid testing, 2004 through 2009

BACKGROUND: United Arab Emirates (UAE) has a heterogeneous population consisting of more than 160 nationalities and 85% of the population being non‐UAE. In 2007, Dubai Blood Donation Centre (DBDC), the major local supplier of blood in the UAE, introduced six‐minipool nucleic acid test (NAT) for hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV), which in 2008 upgraded to individual‐donation (ID)‐NAT. The aim of this study was to analyze the efficacy of the donor screening program in the UAE and evaluate the impact of NAT on the yield and residual risk of transfusion‐transmissible viral infections (TTVIs). STUDY DESIGN AND METHODS: A total of 169,781 blood donations collected at DBDC between 2004 and 2009 were screened for TTVIs. During the period 2008 through 2009, a total of 59,283 donations were tested with both ID‐NAT and serologic assays. The incidence, prevalence, and residual risk for each viral agent were estimated and analyzed. RESULTS: The individual prevalences of HBV, HCV, and HIV per 100,000 donation were 234.4, 110, and 4, respectively. Calculated residual risk per million donations for HBV was decreased from 1.41 in pre‐NAT period to 0.92 in post‐NAT period. These figures were decreased for HCV and HIV from 1.73 and 0.39 to 0 and 0.32, respectively. CONCLUSION: Incidence rates and estimated residual risk indicate that the current risk of TTVIs attributable to blood donation is relatively low in the UAE. The study recommends the parallel use of both serology and ID‐NAT TTVIs screening in blood donations and suggests the exclusion of antibody to hepatitis B core antigen–positive donations as this can eliminate the potential infectivity of these units with marginal effects on the blood stock in UAE.     

Hepatitis B virus (HBV) DNA screening of blood donations in minipools with the COBAS AmpliScreen HBV test

BACKGROUND: The risk of hepatitis B virus (HBV) transmission by blood transfusion (estimated at 1 in 63,000-1 in 205,000 units in the United States) exceeds that of hepatitis C virus (HCV) or human immunodeficiency virus (HIV). Reduction of window-period HBV transmissions through detection of HBV DNA-positive units by minipool nucleic acid testing (MP NAT) would be expected to decrease this risk. STUDY DESIGN AND METHODS: A large multicenter study of the COBAS AmpliScreen HBV test (Roche Molecular Systems) was conducted on minipools of 24 blood donation specimens. The yield of HBV DNA-positive, hepatitis B surface antigen (HBsAg)-negative window-period donations was determined relative to current and newly licensed HBsAg assays. Donors with selected HBV DNA, HBsAg, and anti-hepatitis B core antigen (HBc) results were further evaluated. RESULTS: The detection rate of window-period units was 1 in 352,451 (95% confidence interval, 1 in 2,941,176-1 in 97,561). Assay specificity was high (99.9964%). HBV DNA was detected in 84 percent of HBsAg-positive, anti-HBc-positive donations by MP NAT and in 94 percent when individual-donation (ID) NAT was added. HBV DNA was detected in 0.03 percent of HBsAg-negative, anti-HBc-positive donations by MP NAT and in 0.41 percent when ID NAT was added. CONCLUSIONS: Implementation of HBV MP NAT will provide an increment in safety relative to HBV serologic screening, similar to that for HCV and in excess of that for HIV. Our data indicate that the implementation of HBV MP NAT would likely interdict 39 HBV window-period units and prevent 56 cases of transfusion-transmitted HBV infection annually. The current data indicate that HBV MP NAT should not lead to discontinuation of anti-HBc testing but that discontinuation of HBsAg testing with retention of anti-HBc testing may be possible.     

West Nile virus infection in blood donors in the New York City area during the 2010 seasonal epidemic

BACKGROUND: A uniform threshold strategy for converting from minipool (MP)‐nucleic acid testing (NAT) to individual donation (ID)‐NAT screening for acute West Nile virus (WNV) infection among blood donors is lacking. We report on WNV screening at the New York Blood Center during the 2010 seasonal WNV epidemic, the most severe epidemic in that state since the original outbreak in 1999. STUDY DESIGN AND METHODS: Between July 1 and October 31, 2010, blood donations were screened by MP‐NAT or ID‐NAT and the presence of anti‐WNV immunoglobulin (Ig)M and IgG was evaluated among NAT‐positive donations. RESULTS: Twenty presumed viremic donations were identified for a frequency of 0.0129% (1 in 7752 donations). Nine donations that could have been missed by MP‐NAT were identified. Two of these donations were both IgM and IgG negative, one of which would have been missed if more than one positive donation was required for initiating ID‐NAT. Retrospective ID‐NAT revealed two positive donations. The majority of the NAT‐positive donations in New York (16/19) were from donors who lived in counties that had the highest incidence of human WNV cases in the state. CONCLUSION: Our data details the identification of WNV NAT‐positive blood donations during a severe seasonal epidemic in the New York area. By initiating ID‐NAT after one positive donation, using retrospective testing, and triggering ID‐NAT regionally, we were able to prevent the release of presumably infectious donations. The detection of NAT‐positive donations with retrospective testing, however, may indicate the need for changes in our trigger criteria.     

West Nile virus in 2006 and 2007: the Canadian Blood Services' experience

BACKGROUND: The Canadian blood supply has been screened for West Nile virus (WNV) since 2003. A strategy for targeted individual‐donation nucleic acid testing (ID‐NAT) was implemented in 2004 to identify potentially infectious donations that may be missed by minipool (MP) testing. In 2007, Canada experienced a larger epidemic than in previous years providing an opportunity to evaluate the ID‐NAT triggering algorithm in higher‐risk areas. STUDY DESIGN AND METHODS: A specially created database and internal‐external communication identified regions for targeted ID‐NAT using MP and community triggers. WNV‐positive donations identified by ID‐NAT were reexamined in MP to assess the efficacy of targeted ID‐NAT in identifying potentially infectious donations that may have been missed by MP testing. WNV‐positive donation data from 2006 and 2007 were analyzed to examine temporal and geographic trends. A telephone survey about symptoms was carried out after the 2007 season. RESULTS: In total 78 WNV‐positive donations were identified (66 true‐positives and four false‐positives being in 2007). Most positive donations were in the late summer, concentrated in the same western provinces as community cases. Fifty‐two donations were identified by ID‐NAT and 46% were consistently positive in MP. Of the other 54%, 74% were immunoglobulin (Ig)M‐ and/or IgG‐positive. Fifty‐six percent of donors experienced mostly mild symptoms before or after donation (but all said they were well at the time of donation). CONCLUSION: WNV‐positive donations correspond geographically with the epidemic. MP testing identifies most potentially infectious donations with a smaller potential benefit from targeted ID‐NAT. Mild symptoms are common but may not deter donation.     

Hepatitis B virus transmission by blood transfusion during 4 years of individual-donation nucleic acid testing in South Africa: estimated and observed window period risk

BACKGROUND: Since October 2005, a total of 2,921,561 blood donations have been screened by the South African National Blood Service for hepatitis B virus (HBV) by individual‐donation nucleic acid testing (ID‐NAT). Over 4 years, 149 hepatitis B surface antigen–negative acute‐phase HBV NAT–positive donations were identified (1:19,608). The lookback program identified one probable HBV transmission. STUDY DESIGN AND METHODS: The complete genomes of HBV isolated from the donor and recipient were sequenced, cloned, and analyzed phylogenetically. The HBV window period (WP) transmission risk was estimated assuming a minimum infectious dose of 3.7 HBV virions and an incidence rate correction factor of 1.34 for transient detectability of HBV DNA. RESULTS: Of 149 acute‐phase HBV NAT yields, 114 (1:25,627) were classified as pre–antibody to hepatitis B core antigen (anti‐HBc) WP and 35 (1:83,473) as post–anti‐HBc WP. The acute‐phase transmission risk in the HBV DNA–negative pre‐ and post–anti‐HBc WPs (of 15.3 and 1.3 days, respectively) was estimated at 1:40,000 and 1:480,000, respectively. One HBV transmission (1:2,900,000) was identified in a patient who received a transfusion from an ID‐NAT–nonreactive donor in the pre–anti‐HBc WP. Sequence analysis confirmed transmission of HBV Subgenotype A1 with 99.7% nucleotide homology between donor and recipient strains. The viral burden in the infectious red blood cell unit was estimated at 32 (22‐43) HBV DNA copies/20 mL of plasma. CONCLUSION: We report the first known case of transfusion‐transmitted HBV infection by blood screened using ID‐NAT giving an observed HBV transmission rate of 0.34 per million. The estimated pre–acute‐phase transmission risk in the ID‐NAT screened donor population was 73‐fold higher than the observed WP transmission rate.     

NAT for HBV and anti-HBc testing increase blood safety

BACKGROUND: Routine HBV PCR screening of blood donations to our institutes was introduced in January 1997 to complete the NAT screening program for transfusion-relevant viruses. Testing was successively extended to customer transfusion services with a total of 1,300,000 samples tested per year. STUDY DESIGN AND METHODS: Minipools of 96 blood donation samples were formed by automatic pipettors. HBsAg-reactive samples were included. HBV particles were enriched from the minipools by centrifugation. Conventional and in-house TaqMan PCRs were successively applied for HBV amplification. Sensitivity reached 1000 genome equivalents per mL for each individual donation. Confirmatory single-sample and single-sample enrichment PCRs were established with sensitivities of 300 and 5 to 10 genome equivalents per mL, respectively. RESULTS: After screening of 3.6 million donor samples, 6 HBV PCR-positive, HBsAg-negative donations were identified. Two samples were from infected donors who had not seroconverted and four were from chronic anti-HBc-positive low-level HBV carriers. Retesting by single-sample PCR of 432 samples confirmed positive for HBsAg identified 37 donations that were negative in minipool PCR. Donor-directed look-back procedures indicated that no infected donor who had not yet seroconverted was missed by minipool PCR. However, recipient-directed look-back procedures revealed two anti-HBc-positive recipients of HBsAg-negative minipool PCR-negative, anti-HBc-positive and single-sample PCR-positive blood components. After testing randomly selected 729 HBsAg-negative minipool PCR-negative, anti-HBc-positive donors by single-sample enrichment PCR, 7 were identified with < or = 10 HBV particles per mL of donor plasma. CONCLUSION: Minipool PCR testing after virus enrichment was sensitive enough to identify HBsAg-negative donors who had seroconverterd and HBsAg-negative, anti-HBc-positive chronic HBV carriers. HBV NAT in conjunction with anti-HBc screening would reduce the residual risk of transfusion-transmitted HBV infection.     

Residual risk of transfusion‐transmitted hepatitis B virus (HBV) infection caused by blood components derived from donors with occult HBV infection in Japan

BACKGROUND: Nucleic acid amplification testing (NAT) for hepatitis B virus (HBV) during blood screening has helped to prevent transfusion‐transmitted HBV infection (TT‐HBV) in Japan. Nevertheless, 4 to 13 TT‐HBV infections arise annually. STUDY DESIGN AND METHODS: The Japanese Red Cross (JRC) analyzed repository samples of donated blood for TT‐HBV that was suspected through hemovigilance. Blood donations implicated in TT‐HBV infections were categorized as either window period (WP) or occult HBV infection (OBI) related. In addition, we analyzed blood from 4742 donors with low antibody to hepatitis B core antigen (anti‐HBc) and antibody to hepatitis B surface antigen (anti‐HBs) titers using individual‐donation NAT (ID‐NAT) to investigate the relationship between anti‐HBc titer and proportion of viremic donors. RESULTS: Introduction of a more sensitive NAT method for screening minipools of 20 donations increased the OBI detection rate from 3.9 to 15.2 per million, while also the confirmed OBI transmission rate increased from 0.67 to 1.49 per million. By contrast the WP transmission rate decreased from 0.92 to 0.46 per million. Testing repository samples of donations missed by minipools of 20 donations NAT showed that 75 and 85% of TT‐HBV that arose from WP and OBI donations, respectively, would have been interdicted by ID‐NAT. The ID‐NAT trial revealed that 1.94% of donations with low anti‐HBc and anti‐HBs titers were viremic and that anti‐HBc titers and the frequency of viremia did not correlate. CONCLUSIONS: The JRC has elected to achieve maximal safety by discarding all units with low anti‐HBc and anti‐HBs titers that account for 1.3% of the total donations.     

Efficacy of individual nucleic acid amplification testing in reducing the risk of transfusion‐transmitted hepatitis B virus infection in Switzerland,a low‐endemic region

BACKGROUND: The risk of transfusion‐transmitted hepatitis B virus (HBV) in Switzerland by testing blood donors for hepatitis B surface antigen (HBsAg) alone has been historically estimated at 1:160,000 transfusions. The Swiss health authorities decided not to introduce mandatory antibody to hepatitis B core antigen (anti‐HBc) testing but to evaluate the investigation of HBV nucleic acid testing (NAT). STUDY DESIGN AND METHODS: Between June 2007 and February 2009, a total of 306,000 donations were screened routinely for HBsAg and HBV DNA by triplex individual‐donation (ID)‐NAT (Ultrio assay on Tigris system, Gen‐Probe/Novartis Diagnostics). ID‐NAT repeatedly reactive donors were further characterized for HBV serologic markers and viral load by quantitative polymerase chain reaction. The relative sensitivity of screening for HBsAg, anti‐HBc, and HBV DNA was assessed. The residual HBV transmission risk of NAT with or without anti‐HBc and HBsAg was retrospectively estimated in a mathematical model. RESULTS: From the 306,000 blood donations, 31 were repeatedly Ultrio test reactive and confirmed HBV infected, of which 24 (77%) and 27 (87%) were HBsAg and anti‐HBc positive, respectively. Seven HBV‐NAT yields were identified (1:44,000), two pre‐HBsAg window period (WP) donations (1:153,000) and five occult HBV infections (1:61,000). Introduction of ID‐NAT reduced the risk of HBV WP transmission in repeat donors from 1:95,000 to 1:296,000. CONCLUSIONS: Triplex NAT screening reduced the HBV WP transmission risk approximately threefold. NAT alone was more efficacious than the combined use of HBsAg and anti‐HBc. The data from this study led to the decision to introduce sensitive HBV‐NAT screening in Switzerland. Our findings may be useful in designing more efficient and cost‐effective HBV screening strategies in low‐prevalence countries.     

Sensitivity comparison of two Food and Drug Administration-licensed, triplex nucleic acid test automated assays for hepatitis B virus DNA detection and associated projections of United States yield

BACKGROUND: There have been no comparisons of the relative sensitivity of the two Food and Drug Administration–licensed multiplex (MPX) nucleic acid test (NAT) systems (Procleix Ultrio [Gen‐Probe], TIGRIS platform [Novartis]; and cobas TaqScreen MPX [Roche Molecular Systems], cobas s 201 platform [Roche Instrument Center]) for detecting hepatitis B virus (HBV)‐infected donors in minipool sizes (MP) used in the United States. STUDY DESIGN AND METHODS: Routine blood samples from Thailand were obtained from plasma units from 129 hepatitis B surface antigen (HBsAg)‐negative, HBV NAT–yield donations. Blinded US testing included antibody to hepatitis B core antigen (anti‐HBc), NAT using both manufacturers' systems (undiluted‐individual donation [ID], in singlet and diluted 1:6 and 1:16 in triplicate), quantitative antibody to hepatitis B surface antigen, HBV DNA viral loads, and HBV genotyping. HBV yields in the United States were estimated using the incidence/window period (WP) model and compared to the calculated assay sensitivities. RESULTS: Eighty samples were classified as occult HBV (anti‐HBc reactive) and 49 as WP (anti‐HBc nonreactive). For US pool sizes, MPX detected significantly more samples than Ultrio (MPX MP6 vs. Ultrio MP16; p < 0.0001 for occult and WP). Ultrio MP16 results were not statistically different from Ultrio MP6 (p = 0.68 for occult; p = 0.42 for WP). There was no difference between platforms for MP sizes used in most of the world (MPX MP6 vs. Ultrio ID; p = 0.70 for occult and p = 0.34 for WP). Viral loads were higher in WP samples. Modeled yield estimates were consistent with measured assay sensitivity on the Thai donor samples. CONCLUSIONS: As used in the United States, MPX MP6 is more sensitive than Ultrio MP16, but the impact of this difference is mitigated by low numbers of HBV WP infections.     

Occult hepatitis B virus infection in Thai blood donors

BACKGROUND: An evaluation by the National Blood Center, the Thai Red Cross Society, of two commercial multiplex nucleic acid tests (NATs; the Chiron PROCLEIX ULTRIO test and the Roche Cobas TaqScreen MPX test) for screening Thai blood donors for hepatitis B virus (HBV), hepatitis C virus, and human immunodeficiency virus Type 1 identified 175 HBV NAT–reactive/hepatitis B surface antigen (HBsAg)‐negative donors. The classification of the HBV infection of these donors was confirmed by follow‐up testing. STUDY DESIGN AND METHODS: Index samples were tested for HBV serologic markers and HBV viral loads were determined. Donors were followed for up to 13 months and samples were tested with both NAT assays and for all HBV serological markers. RESULTS: Of 175 HBV NAT–yield donors, 72 (41%) were followed. Based on the follow‐up results, the majority of donors who were followed had an occult HBV infection (66.7%), followed by donors with a primary, acute infection (26.4%). The majority of donors in this latter group (20.8%) were in the window period. Three donors (4.2%), who were anti‐HBs positive, had a reinfection or breakthrough infection. CONCLUSION: The majority of donors detected during routine screening, who were HBsAg negative and NAT reactive, had an occult HBV infection, thus validating the decision to introduce NAT for blood donations in Thailand.     

Infectivity of HBV DNA positive donations identified in look-back studies in Hyogo-Prefecture, Japan

Aims/Objectives: To clarify transfusion incidence of hepatitis B virus (HBV) infected blood negative for mini pool‐nucleic acid amplification testing (MP‐NAT). Background: Japanese Red Cross (JRC) blood centres screen donated blood to avoid contamination with HBV. However, a low copy number of HBV may be overlooked. Methods/Materials: In Hyogo‐Prefecture, JRC blood centres screened 787 695 donations for HBV from April 2005 to March 2009. Of these, 685 844 were donations from the repeat donors. To detect the donors with HBV, serological tests, MP‐NAT and/or individual donation (ID)‐NAT were performed. To detect the recipients with transfusion‐transmitted HBV infection (TTHBI), serological analysis and/or ID‐NAT were performed. Results: In this study, 265 of the 685 844 repeat donations were serologically and/or MP‐NAT positive for HBV. Their repository samples from the previous donation were examined in a look‐back study; 13 of the 265 repository samples proved ID‐NAT positive. Twelve recipients were transfused with HBV‐infected blood components derived from 10 of the 13 HBV‐infected donors. Only 1 of the 12 recipients was identified as TTHBI case. Seven of the 12 recipients escaped from our follow‐up study and 4 recipients were negative for HBV during the observation period. Conclusion: On the basis of the look‐back study among the repeat donors in Hyogo‐Prefecture, Japan, donations with HBV‐infected blood negative for MP‐NAT occurred with a frequency of 13 in 685 844 donations (～1/53 000 donations). However, more than half of the recipients transfused with HBV‐infected blood negative for MP‐NAT could not be followed up. It is necessary to establish a more cautious follow‐up system.     

Residual risk of transfusion-transmitted viral infections in Shenzhen, China, 2001 through 2004

BACKGROUND: There are no current estimates of the residual risks of transmission by blood of hepatitis B virus (HBV) or hepatitis C virus (HCV) and human immunodeficiency virus (HIV) in China. Such estimates are an essential prerequisite to monitoring and improving transfusion safety as well as supporting evidence based assessment of the value of implementing new screening interventions. STUDY DESIGN AND METHODS: Viral screening data for donors from Shenzhen, China, for the period 2001 to 2004, were retrospectively analyzed. The data were applied to a published model to estimate the residual risk of transmitting HIV, HBV, and HCV by blood transfusion in Shenzhen, as well as to assess the residual risk reduction value of various new tests. RESULTS: The point estimates for the combined 2003 and 2004 period calculate as 1 in 17,501 for HBV, 1 in 59,588 for HCV, and 1 in 903,498 for HIV. The predicted yield for improved hepatitis B surface antigen (HBsAg) assays, minipool (MP) nucleic acid testing (NAT), and individual-donation (ID) NAT was 6.9, 9.5, and 28.3 per million donations, respectively. The predicted yield for implementing a fourth-generation HCV (antigen-antibody) or MP NAT assay was 13.4 or 14.7 per million donations, respectively. For HIV, the predicted yield for implementing a fourth-generation HIV (antigen-antibody) or MP NAT assay was markedly smaller, 0.25 or 0.65 per million donations, respectively. CONCLUSIONS: Relative to that reported for Western blood systems, the prevalence and the residual risk of HBV and HCV are high, whereas HIV is comparable. Pending a formal cost-effectiveness study for NAT, implementing improved HBsAg and combination HCV antibody-antigen assays in Shenzhen would markedly reduce the residual risk.     

Integration of nucleic acid amplification test results into hepatitis C virus supplemental serologic testing algorithms: implications for donor counseling and revision of existing algorithms

BACKGROUND: The routine use of hepatitis C virus (HCV) nucleic acid amplification testing (NAT) donor screening assays has provided an opportunity for revision of the current HCV supplemental testing algorithm, which requires that recombinant immunoblot assay (RIBA) be performed on every HCV enzyme immunoassay (EIA)-repeat-reactive donation. The FDA has approved variance requests to use a new algorithm that eliminates the need to perform RIBA when HCV NAT results are reactive. Data are provided in support of this new algorithm. STUDY DESIGN AND METHODS: HCV EIA (including signal-to-cutoff optical density ratio), RIBA, and NAT data were compiled from 33.2 million donations screened over an approximately 4-year period by the American Red Cross and Blood Systems Laboratories. Further, donations having specific combinations of HCV EIA, RIBA, and minipool (MP) NAT results were evaluated, with more sensitive individual-donation (ID) NAT, to construct improved counseling messages for donors. RESULTS: Of 47,041 EIA-repeat-reactive donations, 49.3 percent were RIBA-positive, 17.1 percent RIBA-indeterminate, and 33.5 percent RIBA-negative. NAT-reactive rates were 79.2, 2.5, and 0.18 percent for RIBA-positive, -indeterminate, and -negative donations, respectively. The new algorithm classified an additional 1 percent of donations as HCV-infected while at the same time detecting all infections classified as HCV-infected under the current algorithm. An additional 2.4 percent of RIBA-positive, MP NAT-nonreactive donations were reactive when a frozen-thawed aliquot was retested by ID NAT. CONCLUSION: Integrating HCV NAT results with RIBA results for purposes of donor notification allows more appropriate counseling messages to be given to EIA-repeat-reactive donors. The new HCV supplemental algorithm is an acceptable alternative to the current algorithm because it provides equivalent or superior accuracy in formulating donor counseling messages and may also result in reduced costs and more timely notification of infected donors.     

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

BACKGROUND: Studies showing a significant correlation between hepatitis B surface antigen (HBsAg) and hepatitis B virus (HBV) deoxyribonucleic acid (DNA) levels have focused on the HBV seroconversion window period. STUDY DESIGN AND METHODS: HBsAg levels relative to HBV DNA results in 200 HBsAg-positive, anti-hepatitis B core antigen (HBc)-reactive blood donations were analyzed using quantitative polymerase chain reaction (PCR) (detection limit 400 copies/mL), two research PCR assays with increasing sensitivities (65 copies/mL and 1.3 copies/mL, respectively), and a quantitative HBsAg assay; HBsAg and HBV DNA levels were correlated with HBV serologic profiles; and the potential for replacing HBsAg screening with nucleic acid testing (NAT) was analyzed. RESULTS: Serologic profiles for over 90 percent of the donor samples were consistent with chronic HBV infection. Correlation between HBsAg and HBV DNA concentrations was weak (correlation coefficient = 0.33). Thirty-six percent (72/200) of donor samples had DNA levels under 400 copies per mL. Retesting of the 72 samples by more sensitive PCR assays showed that 60 out of 200 (30%) were positive by PCR with sensitivity of 65 copies per mL, whereas 6 out of 200 (3%) required PCR sensitivity of 1.3 copies per mL for positivity. Three percent (6/200) were negative by all three NAT assays. CONCLUSIONS: HBV DNA levels in HBsAg-positive, anti-HBc-reactive blood donations can be extremely low. About 6 percent of donations would be negative by current minipool HBV NAT methods. About 3 percent of donations would remain undetected by sensitive single-donor NAT. These results indicate caution in any consideration of dropping HBsAg screening.     

Transfusion-transmitted human immunodeficiency virus (HIV) from seroconverting donors is rare in England and Wales: results from HIV lookback, October 1995 through December 2008

BACKGROUND: Lookback is considered when human immunodeficiency virus (HIV) is detected in a repeat blood donor in case the immediately previous negative donation was donated in the infectious window period (IWP) or the assay(s) produced a false‐negative result. HIV lookback investigations undertaken by NHS Blood and Transplant and the Welsh Blood Service between October 1995 and December 2008 are described. STUDY DESIGN AND METHODS: Investigations were undertaken into the previous negative donations of 113 HIV‐infected donors, including retrospective testing of archive samples, tracing of components, and identification of recipients who were offered HIV testing when appropriate. Data were collated on HIV seroconverters and outcome of the lookback was summarized. RESULTS: Two previous negative donations given before the introduction of minipool nucleic acid testing (MP‐NAT) screening were confirmed positive by individual retrospective polymerase chain reaction (PCR) testing of the archive specimen. Red blood cell components had been transfused from both donations. One recipient died after transfusion, and the other was alive and tested HIV positive. All 23 (20%) donations previously testing negative by MP‐NAT were confirmed to be PCR negative on individual testing of an archive specimen and none of the tested recipients of these donations had evidence of transfusion‐transmitted HIV. CONCLUSION: The yield of lookback was low with one positive recipient identified over 13 years of surveillance: HIV transmission occurred from a window period donation given before the introduction of MP‐NAT screening and would have been detected using current testing methods. Current residual risk estimates for the United Kingdom predict that HIV lookback will be of limited benefit, as demonstrated by our data.     

Low-level viraemia of hepatitis B virus in an anti-HBc- and anti-HBs-positive blood donor

summary In many countries, screening of hepatitis B virus (HBV) in blood donors is limited to HBsAg testing. However, if anti-HBc testing and sensitive HBV nucleic acid amplification testing (NAT) for routine screening are not prescribed, HBV viraemia might remain unrecognized. A clinically inconspicuous HBsAg-negative 35-year-old female blood donor was detected with anti-HBc antibodies following the introduction of anti-HBc screening of donors. Based on her history, she had seroconverted to anti-HBs positive (titre >7000 IU/L) after vaccination. Blood donations were routinely tested HBV-DNA negative by minipool NAT. The individual donor samples were reinvestigated by an ultrasensitive NAT with a lower detection limit of 3.8 IU/mL. Intermittent HBV viraemia was detected over a 7-year period from this donor, with a concentration ranging from 8 to 260 IU/mL. In the subsequent donor-directed lookback study, no post-transfusion hepatitis was detected. Low-level HBV viraemia in simultaneous anti-HBc- and anti-HBs-positive blood donors could only be identified with enhanced sensitivity individual polymerase chain reaction assays and is not detectable by pool HBV NAT.     

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

BACKGROUND: The risk of transfusion-transmitted human immunodeficiency virus-1 (HIV-1), hepatitis C virus (HCV), and hepatitis B virus (HBV) infections is predominantly attributable to donations given during the early stage of infection when diagnostic tests may fail. In 1997, nucleic acid amplification technique (NAT)-testing was introduced at the German Red Cross (GRC) blood donor services to reduce this diagnostic window period (WP). STUDY DESIGN AND METHODS: A total of 31,524,571 blood donations collected from 1997 through 2005 were screened by minipool NAT, predominantly with pool sizes of 96 donations. These donations cover approximately 80 percent of all the blood collected in Germany during that period. Based on these data, the WP risk in the GRC blood donor population was estimated by using a state-of-the-art mathematic model. RESULTS: During the observation period, 23 HCV, 7 HIV-1, and 43 HBV NAT-only-positive donations were detected. On the basis of these data and estimated pre-NAT infectious WPs, the residual risk per unit transfused was estimated at 1 in 10.88 million for HCV (95% confidence interval [CI], 7.51-19.72 million), 1 in 4.30 million for HIV-1 (95% CI, 2.39-21.37 million), and 1 in 360,000 for HBV (95% CI, 0.19-3.36 million). Based on observed cases of breakthrough infections, the risk of transfusion-related infections may be even lower. CONCLUSION: The risk of a blood recipient becoming infected with HCV, HIV-1, or HBV has reached an extremely low level. Introduction of individual donation testing for HCV and HIV-1 would have a marginal effect on interception of WP donations.