Implementation of donor screening for infectious agents transmitted by blood by nucleic acid technology in Japan

Reducing the risk of hepatitis B virus transfusion-transmitted infection

Before 1970, approximately 6% of multi-transfused recipients acquired a transfusion-transmitted Hepatitis B virus (HBV) infection. The safety improvements since then have been tremendous. From a level of a few infections per 1000 donations, the risk today, depending on the screening algorithm and additional measurements performed, has decreased to around 1:500,000 to 1:1,000,000, an improvement greater than 1000-fold compared to 50 years ago. This enormous gain in safety has been achieved through many factors, including development of increasingly more sensitive Hepatitis B antigen (HBsAg) assays; the adoption in some countries of hepatitis B core antibody (anti-HBc) screening; an improved donor selection procedure; HBV vaccination programs; and finally the introduction of HBV nucleic acid testing (NAT). Because there is a tendency in transfusion medicine to add one safety measure on top of another to approach the ultimate goal of zero risks, costs become increasingly a matter of debate. It is obvious that any new measure in addition to existing methods or measures will have very poor cost effectiveness. Therefore each country needs to perform its own calculation based on the country’s own epidemiology, resources, political and public awareness of the risks, in order to choose the correct and most cost-efficient measures. Ideally, each country would make decisions regarding implementation of additional blood safety measures in the context of both the perceived benefit and the allocation of overall health care resources.

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.

One-year experience of nucleic acid technology testing for human immunodeficiency virus Type 1, hepatitis C virus, and hepatitis B virus in Thai blood donations

BACKGROUND

Blood donations collected at the National Blood Center, the Thai Red Cross Society, Bangkok, in 2007 were tested by nucleic acid amplification technology (NAT) using the Chiron TIGRIS/Procleix Ultrio test and the Roche cobas s 201/cobas TaqScreen multiplex (MPX) test.

STUDY DESIGN AND METHODS

The sensitivity, specificity, and robustness were determined by testing 486,676 seronegative blood donations. Samples from each day of collection were divided into two sets; the odd-numbered samples were tested individually on the TIGRIS and the even-numbered samples were tested in pools of 6 on the cobas s 201. The status of reactive samples was confirmed by duplicate testing of samples from the plasma bag to calculate the test specificity. Reactive samples were tested on the alternate system and followed up.

RESULTS

The analytical sensitivity of both systems met the 95% limits of detection claimed by the respective package inserts. No cross contamination was seen with either system. Test specificity was 99.93 and 99.90% for the Procleix Ultrio and cobas TaqScreen tests, respectively. The NAT yield rates for human immunodeficiency virus Type 1 (HIV-1), hepatitis C virus (HCV), and hepatitis B virus (HBV) were 1:97,000, 1:490,000, and 1:2800, respectively. Several occult HBV donors, the majority of whom were detected by both tests, were also identified. The HIV-1 and HCV window cases were detected with both tests.

CONCLUSION

The performances of the systems and tests indicated that both were acceptable for routine NAT by the National Blood Center, the Thai Red Cross Society. However, the Procleix Ultrio test appeared to be less sensitive than the cobas TaqScreen test for HBV.

Transfusion-transmitted infections

Although the risk of transfusion-transmitted infections today is lower than ever, the supply of safe blood products remains subject to contamination with known and yet to be identified human pathogens. Only continuous improvement and implementation of donor selection, sensitive screening tests and effective inactivation procedures can ensure the elimination, or at least reduction, of the risk of acquiring transfusion transmitted infections. In addition, ongoing education and up-to-date information regarding infectious agents that are potentially transmitted via blood components is necessary to promote the reporting of adverse events, an important component of transfusion transmitted disease surveillance. Thus, the collaboration of all parties involved in transfusion medicine, including national haemovigilance systems, is crucial for protecting a secure blood product supply from known and emerging blood-borne pathogens.

Sensitivity of hepatitis B virus DNA transcription-mediated amplification testing in hepatitis B surface antigen-positive blood donations

BACKGROUND

The objective was to evaluate the performance of nucleic acid testing (NAT) in the detection of hepatitis B virus (HBV) infection in hepatitis B surface antigen (HBsAg)-positive blood donations.

STUDY DESIGN AND METHODS

A total of 253 HBsAg- and anti-hepatitis B core antigen (HBc)-positive samples (50 hepatitis B e antigen [HBeAg]-positive and 203 anti-HBe-positive) from blood donations collected in France were studied. The samples were investigated with a blood screening assay (Procleix Ultrio, Chiron/Gen-Probe) in minipool (MP; x8) and in individual-donation (ID) testing. All nonreactive samples were retested once, and nonreactive MP samples were assayed for viral load (VL).

RESULTS

All 50 HBeAg-positive samples were reactive in MP-NAT and ID-NAT. Of the 203 anti-HBe-positive donations, 80.3 percent were MP- and ID-reactive, 17.2 percent were MP-nonreactive and ID-reactive, and 2.5 percent were nonreactive in ID-NAT. Overall the sensitivity of ID-NAT was 98 percent versus 84 percent for MP-NAT. After retesting, 16 of the 35 MP-nonreactive and/or ID-reactive donations became MP-reactive and 2 of the ID-nonreactive donations became NAT-reactive. The capacity of Procleix Ultrio to detect HBV DNA was not related to HBsAg subtype, but correlated with the VL: the mean VL in the group of MP-nonreactive samples was 1,420 copies per mL vs. 17,000 copies per mL in the group of 40 MP-reactive samples.

CONCLUSION

These results demonstrate that HBV-NAT in ID format is far more effective in detecting viremia in chronic HBsAg carriers than in MP-NAT. The sensitivity of the NAT assay needs to be improved to be considered for replacing the current HBsAg assays, especially when anti-HBc testing is not performed.

Hepatitis B virus blood screening: unfinished agendas

The risk of transfusion-transmitted hepatitis B virus (TTHBV) has been steadily reduced through the use of volunteer donors, enhanced donor questioning, and increasingly sensitive hepatitis B surface antigen (HBsAg) tests. In a few countries, screening by antibody to hepatitis B core antigen (anti-HBc) and/or hepatitis B virus (HBV) nucleic acid amplification tests (NAT) has also been introduced. Nevertheless, the risk of TTHBV in most countries is higher than the risk of either human immunodeficiency virus-1 (HIV-1) or hepatitis C virus (HCV). HBV screening practices vary both in terms of the markers screened and the tests employed, and are often dependent on a country's healthcare resources. Anti-HBc screening could be employed as an additional safety feature in HBV low-prevalence countries, but would lead to the rejection of a high percentage of otherwise acceptable donations in HBV moderate- and high-prevalence countries. It has been argued that only individual-donor HBV NAT testing would substantially reduce the risk of TTHBV beyond that achieved by the most sensitive HBsAg tests. However, studies from countries with low, moderate and high HBV prevalence have demonstrated NAT yield from window period- and late stage HBV-infected donors, even using minipool testing following the most sensitive HBsAg tests.