Nucleic acid technology screening of Australian blood donors for hepatitis C and human immunodeficiency virus-1 RNA: comparison of two high-throughput testing strategies

Is dual testing for hepatitis C necessary? Modelling the risk of removing hepatitis C antibody testing for Australian blood donations

BACKGROUND AND OBJECTIVES

Parallel testing of blood donations for hepatitis C virus (HCV) antibody and HCV RNA by nucleic acid testing (NAT) has been standard practice in Australia since 2000. Meanwhile, NAT technologies have improved, and HCV has become a curable disease. This has resulted in a significant reduction in the risk and clinical consequences of HCV transmission through transfusion. This study aimed to estimate the residual risk (RR) under various testing options to determine the optimal testing strategy.

MATERIALS AND METHODS

A developed deterministic model calculated the RR of HCV transmission for four testing strategies. A low, mid and high estimate of the RR was calculated for each. The testing strategies modelled were as follows: universal dual testing, targeted dual testing for higher risk groups (first-time donors or transfusible component donations) and universal NAT only.

RESULTS

The mid estimate of the RR was 1 in 151 million for universal dual testing, 1 in 111 million for targeted dual testing of first-time donors, 1 in 151 million for targeted dual testing for transfusible component donations and 1 in 66 million for universal NAT only. For all testing strategies, all estimates were considerably less than 1 in 1 million.

CONCLUSION

Antibody testing in addition to NAT does not materially change the risk profile. Even conservative estimates for the cessation of anti-HCV predict an HCV transmission risk substantially below 1 in 1 million. Therefore, given that it is not contributing to blood safety in Australia but consuming resources, anti-HCV testing can safely be discontinued.

Blood donor deferral for men who have sex with men: still room to move

BACKGROUND

Like a number of other countries, Australia mandates that a man who has had sex with men is deferred from donation until 12 months has elapsed since the sexual activity. This review examined whether this deferral period is justified by current evidence.

STUDY DESIGN AND METHODS

Databases (Medline, EMBASE, Scopus) were searched using terms "blood donation" and "gay" or "MSM" and "HIV risk" from the mid-1980s to the present to investigate the history of donor deferral policy and its rationale in Australia.

RESULTS

Gay and bisexual men in Australia face a higher risk of human immunodeficiency virus and other blood-borne viruses (BBVs) than other populations. All blood donations, however, are tested for BBVs, and with current testing technologies the window period during which infection may be present but not detected is now less than 1 week. While there is a moral imperative to maintain blood safety, there is also a moral imperative to ensure that differential treatment of population groups with regard to donation eligibility is scientifically justified. Potential social harms that may flow from a dissonance between deferral policy and its evidence base include loss of trust and increased nonadherence to policy.

CONCLUSIONS

A 12-month deferral for gay and bisexual men exceeds what is required to maintain blood safety. This disparity potentially causes social harm without any additional benefit to public health. Reducing the deferral period to 3 months will not increase health risk to recipients and may have the social benefit of increasing inclusiveness.

Re-examining blood donor deferral criteria relating to injecting drug use

BACKGROUND AND AIMS

Potential Australian blood donors are deferred indefinitely if they report a history of injecting drug use (IDU), or for 12 months if they report having engaged in sexual activity with someone who might have ever injected. Given incremental improvements in blood safety, this study sought to examine whether Australia's IDU-related eligibility criteria reflected current scientific evidence, were consistent with international best practice and, if current IDU-related policies were to be changed, how this should happen.

METHODS

An expert committee was formed to review relevant literature with a focus on issues including: the epidemiology of IDU in Australia and key transfusion-transmissible infections (TTIs) among Australian people who inject drugs (PWID); and, 'non-compliance' among PWID regarding IDU-related blood donation guidelines. International policies relating to blood donation and IDU were also reviewed. Modelling with available data estimated the risk of TTIs remaining undetected if the Blood Service's IDU-related guidelines were changed.

RESULTS

Very few (<1%) Australians engage in IDU, and IDU risk practices are reported by only a minority of PWID. However, the prevalence of HCV remains high among PWID, and IDU remains a key transmission route for various TTIs. Insufficient data were available to inform appropriate estimates of cessation and relapse among Australian PWID. Modelling findings indicated that the risk of not detecting HIV becomes greater than the reference group at a threshold of non-admission of being an active PWID of around 1.8% (0.5-5.1%). Excluding Japan, all Organisation for the Economic Co-operation and Development member countries permanently exclude individuals with a history of IDU from donating.

CONCLUSION

Numerous research gaps meant that the study's expert Review Committee was unable to recommend altering Australia's current IDU-related blood donation guidelines. However, having identified critical knowledge gaps and future areas of research, the review made important steps toward changing the criteria.

Hepatitis B virus nucleic acid amplification testing of Australian blood donors highlights the complexity of confirming occult hepatitis B virus infection

BACKGROUND

We present an analysis of the first 2 years of hepatitis B virus (HBV) nucleic acid testing (NAT) of the Australian donor population.

STUDY DESIGN AND METHODS

Between July 5, 2010, and July 4, 2012, all blood donations were screened for HBV DNA and hepatitis B surface antigen (HBsAg). Donors who tested HBsAg negative but HBV NAT positive were assessed as occult hepatitis B infections (OBI) if reactive for antibodies to HBV core antigen (anti-HBc). Donors who were anti-HBc reactive but with nonrepeatable or nondiscriminated NAT results were assessed as HBV inconclusive pending follow-up testing.

RESULTS

During the study period a total of 2,673,521 donations were screened for HBV. Forty-two chronic OBI infections (5.55/100,000 donors) were identified compared to eight acute serologic window period infections (1.06/100,000 donors). Of the 42 OBI cases, 23 (54.8%) were detected the first time they were screened for HBV DNA while 19 (45.2%) gave one or more HBV NAT-nonreactive results before detection. Of 68 donors initially assessed as HBV inconclusive and available for follow-up, 10 later confirmed as OBI cases while 51 were NAT nonreactive but remained anti-HBc reactive and OBI could not be excluded.

CONCLUSION

This study demonstrated a substantially higher prevalence of OBI compared to acute serologic window period HBV infections in Australian blood donors. Follow-up testing of OBI cases indicates that HBV DNA is often only intermittently detectable in OBI, highlighting the importance of including anti-HBc to optimize the HBV testing algorithm.

Screening of HIV infection: role of molecular and immunological assays

Due to technical improvements and new developments of immunological assays, the reliability of serological laboratory diagnosis of HIV infection has improved considerably and the residual risk, due to the diagnostic window for transfusion-transmitted HIV, has been reduced significantly. Through the addition of nucleic acid amplification tests (NAT) to blood donor screening, the residual risk can de further decreased by up to 50%, depending on the sensitivity of the NAT protocol and whether individual or pooled blood donations are screened. In-house and commercially available NAT have been implemented in blood banks as HIV only or multiplexed HIV and hepatitis B or C virus assays. As an alternative to separate antigen and antibody screening, combined fourth-generation assays have been developed in 1997, and have achieved a high degree of sensitivity and specificity. Thus, they can replace stand-alone antigen and third-generation antibody assays. While they are used in the routine diagnostics of HIV infection in many countries throughout the world, they probably represent no alternative for NAT in blood-donor screening in industrialized countries. In the next few years, technical improvements will further simplify NAT screening. While there is still some potential to improve the detection threshold of NAT, the sensitivity of the antigen module of fourth-generation assays (a lowest concentration of 3-5 pg of p24 antigen) is probably very close to its technical limit.

Trends in transfusion-transmissible infections among Australian blood donors from 2005 to 2010

BACKGROUND

Routine monitoring of trends in transfusion-transmissible infections (TTIs) is essential to maintaining and improving transfusion safety. Although periodic studies have been published there is no comprehensive trend analysis for TTIs in Australian donors. This study determined recent trends in TTIs for which testing is conducted in Australia and described key attributes of infected blood donors.

STUDY DESIGN AND METHODS

This is a retrospective analysis using data on donation testing for TTIs (2005-2010) from the national blood service donor database and data on postdonation interviews with TTI-positive donors (2008-2010) from a risk factor database incorporating responses to standardized interview questions. The study measured the prevalence and incidence of TTIs in Australia and assessed their time trends. Multivariate analysis of time trends was conducted using Poisson regression models.

RESULTS

Overall, the prevalence and incidence of TTIs in 2005 to 2010 remained low and steady. The prevalence of hepatitis C virus decreased (rate ratio [RR], 0.93; 95% confidence interval [CI], 0.89-0.97) and the prevalence of active syphilis increased (RR, 1.51; 95% CI, 1.15-1.99) significantly during the study period. Prevalence of TTIs among Australian blood donors was substantially lower than that in the general population and no unique risk factors were identified in test-positive blood donors when compared with the general population.

CONCLUSION

Both the prevalence and the incidence of TTIs in Australian blood donors remained low, with a steady or declining trend for most infections except active syphilis. The lower prevalence of TTIs in blood donors compared with the general population reflects the effectiveness of donor education and donor selection measures in Australia.

Analysis of sample-to-cutoff ratios on chemiluminescent immunoassays used for blood donor screening highlights the need for serologic confirmatory testing

BACKGROUND

High sample-to-cutoff (s/co) ratios on hepatitis C virus antibody (anti-HCV) screening immunoassays (IAs) are indicative of confirmed-positive results and, according to some reports, can be used to determine anti-HCV status without the need for confirmatory testing. The purpose of this study was to determine whether s/co ratios on hepatitis B surface antigen (HBsAg), antibody to human immunodeficiency virus Types 1 and 2 (anti-HIV-1/2), anti-HCV, and antibody to human T-lymphotropic virus Types I and II (anti-HTLV-I/II) chemiluminescent immunoassays (ChLIAs) can be used to discriminate between biologic false-reactive (BFR) and confirmed-positive results.

STUDY DESIGN AND METHODS

In a blood donor population the s/co ratio distributions for BFR and confirmed-positive results were compared for the Abbott PRISM HBsAg, HIV O Plus, HCV, and HTLV-I/II ChLIAs to determine the extent of overlap between the two distributions for each assay.

RESULTS

The s/co ratio distributions for BFR and confirmed results overlapped in the range of 10.00 to 60.00, 1.00 to 6.00, 3.00 to 15.00, and 1.00 to 100.00 for the PRISM HIV O Plus, HCV, HTLV-I/II, and HBsAg assays, respectively.

CONCLUSION

Although high s/co ratios were predictive of confirmed-positive results in all four assays, a number of confirmed-positive samples gave low values while some biologic false-positive samples showed high values. As the s/co ratio distributions for BFR and confirmed-positive results overlapped for all four PRISM assays, this study highlights the importance of serologic confirmatory testing and the need for caution when using screening IA results to assign a final donor status.

Emerging viral threats to the Australian blood supply

OBJECTIVES

To assess the risk to the Australian blood supply posed by emerging or re-emerging viral infections.

METHOD

A review was undertaken of the English-speaking literature on the potential for emerging viral threats to human health in Australia, the future implications of virus ecology, climate change and population movement and the implications for blood transfusion.

RESULTS

Published data confirm that Australia's blood supply is among the safest in the world for currently screened viral pathogens as a result of rigorous surveillance, donor selection and state-of-the-art processing and laboratory testing. However, Australia has a number of other viral pathogens with the potential to threaten the safety of the blood supply such as the Ross River, Barmah Forrest, Kunjin, Japanese Encephalitis, Murray Valley Encephalitis and dengue viruses. Of these, dengue is currently of most concern to blood safety because; it can cause fatalities, there are regular seasonal outbreaks in Northern Australia and, in contrast to other viruses mentioned above an overseas case of transfusion transmission has already been documented. Notably, despite the lack of a suitable dengue screening test the ARCBS already implements supplementary measures to protect the blood supply during outbreaks.

CONCLUSION

Current interventions have proven extremely effective in minimising transfusion transmission in Australia of recognised viral pathogens. The threat posed by emerging viral pathogens to the safety of blood transfusion emphasises the need for global collaboration and consideration of further intervention strategies on a country by country basis including options such as nucleic acid testing and pathogen reduction technologies.

Estimating the risk of blood donation associated with HIV risk behaviours

A blood donor questionnaire and declaration, with deferral of potential donors at a higher risk of blood-borne infections, was introduced in Australia in the mid-1980s to reduce the risk of donation of HIV-infected blood. However, the absolute risk of HIV transmission through blood donation from high-HIV-risk donors has not been estimated. This study presents a new method of assessing the risk posed to the blood supply by selected HIV risk behaviours. A model was developed to estimate the probability of blood donation during the window period for HIV infection. Five scenarios for blood donors were considered: (1) men who have sex with men (MSM), (2) men who have sex with women in Australia, (3) women who have sex with partners from countries with a high HIV prevalence, (4) men who have sex with commercial sex workers in Australia and (5) people injecting drugs used once in a year. Those estimated to be at highest risk of becoming infected and donating in the window period were MSM. Women who have sex with men from countries of high HIV prevalence are at greater risk than men who have sex with female sex workers from Australia. These three groups under current Australian guidelines are deferred from donating blood for 12 months. In Australia, a single episode of injecting drug use is associated with very low risk of HIV transmission. The model presented in this study can be used to assess the impact of selected individual risk behaviours on the safety of the blood supply.

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

BACKGROUND

Recently developed nucleic acid testing (NAT) assays incorporating simultaneous detection of human immunodeficiency virus (HIV), hepatitis C virus (HCV), and hepatitis B virus (HBV) have made HBV NAT screening more feasible for blood services. This study compared the performance of two "multiplex" NAT assays and their automated testing platforms.

STUDY DESIGN AND METHODS

The HBV NAT yield rate was estimated by testing 10,397 Hong Kong (HK) donor samples concurrently on the PROCLEIX ULTRIO (Ultrio) assay as individual donor samples with the TIGRIS and on the cobas TaqScreen multiplex (cobas MPX) test in pools of 6 with the cobas s 201. Analytical sensitivity was assessed by probit analysis of diluted international standards and operational performance was compared.

RESULTS

Each system detected two different HBV NAT yield samples for a combined rate of 0.04 percent. One additional sample was reactive on the cobas MPX test but remained unresolved. The 95 percent detection limits for HIV-1, HBV, and HCV were 42.2, 12.2, and 2.0 IU per mL, respectively, for Ultrio and 50.5, 8.4, and 6.0 IU per mL for the cobas MPX. The invalid test and failed run rates were 0.05 and 2.92 percent, respectively, for the TIGRIS and 2.39 and 5.53 percent for the cobas s 201.

CONCLUSION

Clinical sensitivity for HBV in HK blood donors was equivalent, as was the analytical sensitivity for HIV-1 and HBV; however, the Ultrio assay had a higher analytical sensitivity for HCV. Despite a shorter downtime and mean time of repair for the cobas s 201, the TIGRIS demonstrated better overall operational performance.

Development, validation and evaluation of a homogenous one-step reverse transcriptase-initiated PCR assay with competitive internal control for the detection of hepatitis C virus RNA

Nucleic acid amplification testing for hepatitis C virus (HCV) RNA has become an essential tool for the prevention and clinical management of hepatitis C. We describe the development, validation and evaluation of a homogenous reverse transcriptase-initiated HCV-PCR assay with competitive internal control that is applicable to both the quantitative detection of HCV genomes in single patient samples and the screening of blood donations by mini-pool testing. For the implementation of a positive run control, a HCV RNA-positive plasma sample was calibrated against an international HCV RNA standard preparation. For quantification purposes, an in vitro-transcribed RNA calibrator sequence was used. The detection limit of the assay (95% positive cut-off) was determined by probit analysis and was calculated as 114 IU/mL. Comparable sensitivity to different HCV template sequences was verified for HCV genotypes 1-5. Quantitative test results correlated well with viral loads that had been previously determined by the Bayer VERSANT HCV RNA 3.0 bDNA assay (n=53, R=0.943, p<0.001). During more than 5 years of blood donation testing, the specificity of the assay was found to be 99.51%. All assay components showed constant performance during this time period. In conclusion, we introduce a well-proven method that allows fast and reliable quantification of HCV genomes.

Follow-up of six blood donors highlights the complementary role and limitations of hepatitis C virus antibody and nucleic acid amplification tests

BACKGROUND AND OBJECTIVES

The purpose of this study was to analyse the follow-up results for six blood donors who screened positive for hepatitis C virus (HCV) by nucleic acid amplification technology (NAT) but were non-reactive in the primary antibody immunoassay (HCV NAT yield).

MATERIALS AND METHODS

Volunteer blood donations were screened, in parallel, for antibodies to hepatitis C virus (anti-HCV) and for human immunodeficiency virus (HIV)/HCV RNA using the Abbott PRISM HCV Chemiluminescent immunoassay (ChLIA) and the Chiron Procleix HIV-1/HCV RNA assays, respectively. NAT yield donor samples were further tested using supplemental assays, including an alternate HCV antibody enzyme immunoassay (EIA) (Abbott Murex anti-HCV Version 4), an immunoblot (Ortho RIBA-3 or Genelabs Diagnostics HCV Blot 3.0) and two alternative HCV NAT assays [Roche HCV Amplicor and an assembled HCV polymerase chain reaction (PCR)]. Five of the six donors were available for follow-up testing.

RESULTS

The six NAT yield donations were identified as constituents of 24-member minipools among 2,212,695 donations screened over the 28-month study period. All samples were positive when tested, undiluted, using the Roche Amplicor and assembled reverse transcription-polymerase chain reaction (RT-PCR) alternate NAT assays. One of the donors, subsequent to seroconversion, showed RNA levels that fluctuated above and below the limit of detection of the NAT screening assay. Three of the six were reactive on the secondary EIA and showed reactivity to the core c22(p) antigen by immunoblot at the index donation. Two others subsequently became reactive in the ChLIA prior to the EIA, showing reactivity against c100 and/or c33c antigens by immunoblot. The remaining donor became reactive in the ChLIA and EIA at the same time, showing RIBA reactivity against all of the following three peptides: c100; c33c; and c22(p).

CONCLUSIONS

This study demonstrated that at least five of six HCV NAT yield donors were in the pre- or early antibody seroconversion phase of infection. The observation that one yield donor demonstrated HCV RNA that fluctuated above and below the limit of detection of the primary NAT-screening assay supports the maintenance of both NAT and antibody screening for HCV. Follow-up testing of suspected yield donors revealed that the primary and alternate anti-HCV immunoassays had different performance characteristics, depending on the specificity of the donor's early anti-HCV response.