Multicenter performance evaluation of a transcription-mediated amplification assay for screening of human immunodeficiency virus-1 RNA, hepatitis C virus RNA, and hepatitis B virus DNA in blood donations

Accuracy of quantitative HIV-1 RNA test methods at 1000 copies/mL and the potential impact of differences in assay calibration on therapy monitoring of patients

The World Health Organization (WHO) recommends the clinical use of a human immunodeficiency virus 1 (HIV-1) viral load (VL) threshold level of 1000 copies (cp)/mL in patients on antiretroviral therapy (ART) to distinguish between viral control (VL < 1000 cp/mL) and viral failure or poor adherence (VL > 1000 cp/mL). The accuracy of five quantitative HIV-1 RNA assays at this level was compared by replicate testing (n = 24) of 1000 cp/mL samples prepared from the Viral Quality Control (VQC) HIV-1 subtype B standard, which is in use for validation of nucleic acid testing methods since 1995. Until 2004 the VL assays reported geometric mean (95% confidence interval [CI]) values ranging between 449 (188-1067) and 3162 (3057-2367) cp/mL when using the Siemens bDNA 3.0 assay as reference method for an assigned value of 1000 (962-1038) cp/mL. In 2018, the following values (95% CI) were found by 24 replicate tests in each of the VL assays on the 1000 cp/mL samples: Abbott RealTime 1084 (784-1572), BioMerieux EasyQ 1110 (533-2230), Roche CAP/CTM 1277 (892-1828), Hologic Aptima 1616 (1324-1973), and Cepheid GeneXpert 2502 (1713-3655) cp/mL. Calibration studies involving three consecutive WHO replacement standards showed a significant drift in the amount of RNA copies per International Unit overtime. Heat inactivation of HIV-1 standards was found to cause a destandardizing effect. Our study underlines the limitations in HIV-1 RNA assay calibration based on frequently replaced WHO international standards. It is therefore proposed that clinicians interpret the recommended 1000 cp/mL alert level in therapy monitoring with an inaccuracy range of 500 to 2000 cp/mL.

Evaluation of the Aptima HIV-1 Quant Dx Assay for HIV-1 RNA Quantitation in Different Biological Specimen Types

The search for a cure for HIV infection has highlighted the need for increasingly sensitive and precise assays to measure viral burden in various tissues and body fluids. We describe the application of a standardized assay for HIV-1 RNA in multiple specimen types. The fully automated Aptima HIV-1 Quant Dx assay (Aptima assay) is FDA cleared for blood plasma HIV-1 RNA quantitation. In this study, the Aptima assay was applied for the quantitation of HIV RNA in peripheral blood mononuclear cells (PBMCs; n = 72), seminal plasma (n = 20), cerebrospinal fluid (CSF; n = 36), dried blood spots (DBS; n = 104), and dried plasma spots (DPS; n = 104). The Aptima assay was equivalent to or better than commercial assays or validated in-house assays for the quantitation of HIV RNA in CSF and seminal plasma. For PBMC specimens, the sensitivity of the Aptima assay in the detection of HIV RNA decayed as background uninfected PBMC counts increased; proteinase K treatment demonstrated some benefit in restoring signal at higher levels of background PBMCs. Finally, the Aptima assay yielded 100% detection rates of DBS in participants with plasma HIV RNA levels of ≥35 copies/ml and 100% detection rates of DPS in participants with plasma HIV RNA levels of ≥394 copies/ml. The Aptima assay can be applied to a variety of specimens from HIV-infected subjects to measure HIV RNA for studies of viral persistence and cure strategies. It can also detect HIV in dried blood and plasma specimens, which may be of benefit in resource-limited settings.

Evaluation of the Procleix Ultrio Elite Assay and the Panther-System for Individual NAT Screening of Blood, Hematopoietic Stem Cell, Tissue and Organ Donors

BACKGROUND

The performance of the multiplex Procleix Ultrio Elite assay as individual donor nucleic acid test (ID-NAT) for the detection of HIV-1, HIV-2, HCV, and HBV was evaluated in a retrospective, single center study.

METHODS

ID-NAT results of 21,181 blood donors, 984 tissue donors, 293 hematopoietic stem cell donors and 4 organ donors were reviewed in synopsis with results of serological screening and additional discriminatory and repetitive NAT in case of positive donors.

RESULTS

Specificity of the initial Procleix Ultrio Elite assay was 99.98% and after discriminatory testing 100.00%. Initially invalid results were observed in 75 of 21,181 blood donors (0.35%) but 16 of 984 tissue donors (1.62%, p < 0.001) which included non-heart-beating ('cadaveric') donors. All these had valid negative ID-NAT results after repeated testing or testing of 1:5 diluted specimens in case of tissue donors. Occult hepatitis B (defined here as HBV DNAemia without HBsAg detection) was demonstrated by ID-NAT in two anti-HBc-positive tissue donors and suspected in two other tissue donors, where a definite diagnosis was not achieved due to the insufficient sample volumes available.

CONCLUSION

The Procleix Ultrio Elite assay proved to be specific, robust and rapid. Therefore, routine ID-NAT may also be feasible for organ and granulocyte donors.

Aptima HIV-1 Quant Dx--A fully automated assay for both diagnosis and quantification of HIV-1

BACKGROUND

Separate assays are available for diagnosis and viral load (VL) monitoring of HIV-1. Studies have shown that using a single test for both confirmatory diagnosis and VL increases linkage to care.

OBJECTIVE

To validate a single assay for both diagnosis and VL monitoring of HIV-1 on the fully automated Panther platform.

STUDY DESIGN

Validate the assay by assessing specificity, sensitivity, subtype detection, seroconversion, reproducibility and linearity. Also assess diagnostic agreement with the Procleix(®) Ultrio Elite™ discriminatory assay (Procleix), and agreement of VL results (method comparison) with Ampliprep/COBAS TaqMan HIV-1 version 2.0 (CAP/CTM), using clinical samples.

RESULTS

The assay was specific (100%) and sensitive with a 95% limit of detection of 12 copies/mL with the 3rd WHO standards. Aptima detected HIV in seroconversion panels 6 and 11 days before p24 antigen and antibody tests, respectively. Diagnostic agreement with Procleix, was 100%. Regression analysis showed good agreement of VL results between Aptima and CAP/CTM with a slope of 1.02, intercept of 0.07, and correlation coefficient (R(2)) of 0.97. Aptima was more sensitive than CAP/CTM. Equivalent quantification was seen on testing clinical samples and isolates belonging to HIV group M, N, O and P and commercially available subtype panels. Assay results were linear (R(2) 0.9994) with standard deviation of <0.17 log copies across assay range.

CONCLUSIONS

The good specificity, sensitivity, precision, subtype performance and clinical agreement with other assays demonstrated by Aptima combined with the complete automation provided by the Panther platform makes Aptima a good candidate for both VL monitoring and diagnosis of HIV-1.

New Strategies for Blood Donor Screening for Hepatitis B Virus

Serologic testing for hepatitis B virus (HBV) surface antigen (HBsAg) and antibody to HBV core antigen (anti-HBc) has historically been the foundation of blood screening, while HBV nucleic acid testing (NAT) was recently developed to detect HBsAg-negative, anti-HBc-negative blood units donated during early acute infection. Comparison data on seroconversion panels using HBsAg assays of varying sensitivities and pooled- or single-sample NAT, along with viral load estimates corresponding to HBsAg assay detection limits, have provided information on the theoretical benefits of NAT relative to HBsAg. Model-derived estimates have generally been predictive of the yields of DNA-positive, HBsAg-negative window period blood units detected in a number of studies from Europe, Japan, and the US. Studies indicate that the added benefit of pooled-sample NAT is relatively small in areas of low endemicity, with greater yields in areas highly endemic for HBV. Single-sample NAT would offer more significant early window period closure and could prevent a moderate number of residual HBV transmissions not detected by HBsAg assays; however, no fully automated single-sample HBV NAT systems are currently available.Even single-sample HBV NAT may not substitute for anti-HBc screening, as indicated by studies of donors with isolated anti-HBc who have extremely low DNA levels undetectable by standard single-sample NAT and who have been associated with transfusion-transmitted HBV. Moreover, HBsAg testing may still be needed even in the setting of combined anti-HBc and NAT screening. HBsAg-positive units from donors in the chronic stage of infection may contain very low or intermittently detectable DNA levels that single-sample NAT would miss. Although such donors are usually anti-HBc reactive and would be interdicted by anti-HBc screening, some lack anti-HBc. Extensive parallel testing will be needed to determine whether single-sample NAT in combination with anti-HBc might be sufficient to detect all the infectious donors currently interdicted by HBsAg testing. In countries that do not screen for anti-HBc, HBsAg testing would be the only means of detecting donations from chronically infected individuals with low/intermittently detectable DNA, since even single-donor NAT would not identify these potentially infectious blood units. In the future, the current fully automated HBsAg assays may incorporate significant sensitivity improvements, and automated single-sample HBV NAT may become a reality. Each country will need to develop its blood screening strategy based on HBV endemicity, yields of infectious units detected by different serologic/NAT screening methods, and cost effectiveness of test methods in ensuring blood safety.

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.

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.

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.

The efficacy of individual-donation and minipool testing to detect low-level hepatitis B virus DNA in Taiwan

BACKGROUND

Financial constraints are the main concern in implementing nucleic acid testing (NAT) as routine blood screening in Taiwan. The PROCLEIX ULTRIO assay (Ultrio) on the TIGRIS System (Novartis Diagnostics) was evaluated for its operational performance both for individual-donation testing (IDT) and in minipools of 4 (MP4) to develop a feasible solution.

STUDY DESIGN AND METHODS

Analytical sensitivity was determined by testing WHO international standards. We tested 10,290 blood donors, 4210 in IDT and 6080 in MP4. Potential hepatitis B virus (HBV) yield donors (hepatitis B surface antigen [HBsAg] negative/NAT reactive) were evaluated for up to 9 months' follow-up. Discordant results between the Ultrio assay and the HBsAg tests were further analyzed by HBV antibody serology, alternative NATs, HBV DNA quantification, and sequencing.

RESULTS

The 95% limits of detection in IU/mL (95% confidence interval) were as follows: human immunodeficiency virus Type 1 (HIV-1), 18 (12-34); hepatitis C virus (HCV), 4.4 (2.8-8.9); and HBV, 6.3 (4.4-11). The retest rates were 0.55% for IDT and 0.33% for MP4. No HIV or HCV yield cases were found, while there were 12 potential HBV yield cases, nine from IDT and three from MP4 testing. Eleven of them were successfully genotyped as B2. Ten of them returned for follow-up and mostly were determined as occult HBV infection (OBI). The IDT yield rate of 9 in 4210 (0.21%) was fourfold greater than the MP4 yield rate of 3 in 6080 (0.05%; p < 0.05).

CONCLUSION

The higher yield rate for IDT versus MP4 demonstrates the benefit to implement a more sensitive NAT strategy in regions having significant OBI carriers such as Taiwan.

Efficacy of hepatitis B virus (HBV) DNA screening and characterization of acute and occult HBV infections among blood donors from Madrid, Spain

BACKGROUND

Screening of blood units for hepatitis B virus (HBV) DNA identifies donations collected during the window period (WP) of the acute infection and may improve viral safety of the blood supply. It also leads to the detection of occult hepatitis B infection (OBI).

STUDY DESIGN AND METHODS

From January 2005 to December 2006, a total of 383,267 blood units were screened for hepatitis B surface antigen (HBsAg) and HBV DNA in two transfusion centers in Madrid, using either individual-donation nucleic acid testing (ID-NAT) or minipool (MP-NAT) of eight donations (MP8). Samples positive for HBV DNA and negative for HBsAg were confirmed by a second molecular test, the viral DNA was quantified, and a genome fragment including the region encoding the major hydrophilic region (MHR) of HBsAg was sequenced.

RESULTS

The overall yield of HBV DNA-positive, HBsAg-negative units was 1 in 21,282 (18 cases), higher when using ID-NAT than MP8-NAT (1:9862 vs. 1:51,011; p < 0.01). Four donations (1/95,817) were collected during the infectious pre-HBsAg WP, one during an early recovery stage, and the remaining 13 (1/29,482) were OBIs, six of whom had no detectable antibody to HBsAg. Low-level Genotype D HBV DNA was detected in all OBI cases; the frequencies of this genotype and MHR amino acid substitutions were significantly higher than reported from unselected Spanish HBsAg carriers. Donors with OBI had normal aminotransferase levels and were significantly older than donors carrying HBsAg.

CONCLUSIONS

Blood donors in the WP and with OBI are not uncommon in Madrid and are detected at a higher frequency with ID-NAT than MP-NAT.

Sensitivity of two hepatitis B virus, hepatitis C virus (HCV), and human immunodeficiency virus (HIV) nucleic acid test systems relative to hepatitis B surface antigen, anti-HCV, anti-HIV, and p24/anti-HIV combination assays in seroconversion panels

BACKGROUND

Accurate determination of the infectious window period (IWP) that remains with individual-donation (ID) or minipool (MP) NAT compared to those with serology assays is essential for residual risk estimations.

STUDY DESIGN AND METHODS

The relative sensitivity of the Procleix Tigris system (Gen-Probe/Chiron) used in ID-NAT format and cobas s 201 (Roche Molecular Systems) applied in 1:6 diluted samples to mimic six-minipool (MP6) nucleic acid test (NAT) was assessed by quadruplicate testing of five seroconversion panels per marker. A mathematical analysis based on the log-linear increase of viremia in the ramp-up phase, as established with bDNA 3.0 assays enabled estimation of the IWP for human immunodeficiency virus (HIV) and hepatitis B virus (HBV) assays.

RESULTS

The mean IWPs were Tigris HIV RNA 5.5 days, s 201 (1:6) HIV RNA 7.4 days, GenScreen Plus p24/anti-HIV 17.8 days, PRISM anti-HIV 19.0 days, Tigris HBV DNA 20.6 days, s 201 (1:6) HBV DNA 22.6 days, Bio-Rad hepatitis B surface antigen (HBsAg) 37.8 days, and PRISM HBsAg 35.5 days. At estimated 50 percent NAT seroconversion rates, s 201 (1:6) and Tigris showed mean window-period reduction times (WPRTs) of 30.5 to 35.5 days to hepatitis C virus antibody (anti-HCV) assays, 10.4 to 13.5 days to anti-HIV, or combination p24/anti-HIV assays and 12.8 to 17.2 days to HBsAg assays.

CONCLUSIONS

Tigris ID-NAT detected HIV RNA 2 days earlier than s 201 MP6-NAT, but the difference in sensitivity between the two NAT systems was not significant in HBV seroconversion panels. Insufficient seroconversion samples were available for reliable modeling of WPRT in early HCV infection, but 1.4 to 2.0 days could be predicted by translating analytical sensitivity data. Both multiplex NAT systems demonstrate significant WPRTs compared to (combined) antigen and antibody assays.

Ultra-high-throughput, automated nucleic acid detection of human immunodeficiency virus (HIV) for infant infection diagnosis using the Gen-Probe Aptima HIV-1 screening assay

The early diagnosis of human immunodeficiency virus (HIV) infection in infants is critical to ensure the initiation of treatment before significant immunological compromise. Each year an estimated 300,000 HIV-exposed infants in South Africa require access to tests for the diagnosis of HIV infection. Currently, testing is performed at several facilities by using PCR amplification of HIV DNA at 6 weeks of age by the use of dried blood spots (DBSs) and whole blood (WB). The Gen-Probe Aptima HIV type 1 (HIV-1) screening assay (the Aptima assay) is a qualitative nucleic acid test based on transcription-mediated amplification (TMA), a technology routinely used in blood banks in South Africa. The performance characteristics of Gen-Probe's TMA technology compared well to those of the Roche Amplicor HIV-1 DNA (version 1.5) assay. The sensitivity of the assay with WB and DBS samples was 100%, and the specificities were 99.4% and 99.5% for DBSs and WB, respectively. The detection of HIV by the Aptima assay at greater levels of dilution in samples negative by the comparator assay indicates an improvement in sensitivity by the use of the TMA technology. The ability to process 1,900 samples in a 24-h period on the Tigris instrument makes the Aptima assay an attractive option for high-volume, centralized laboratories.

Comparison of the analytical and operational performance of two viral nucleic acid test blood screening systems: Procleix Tigris and cobas s 201

BACKGROUND

The operational and analytical performance of two automated triplex hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV) nucleic acid test (NAT) systems were compared in four screening laboratories of the French Blood Service.

STUDY DESIGN AND METHODS

Two laboratories evaluated the Procleix Tigris system (Chiron/Gen-Probe) in individual donation (ID) format and two sites used the cobas s 201 system (Roche Molecular Systems) on minipools (MPs) of six donations. The analytical sensitivity, the specificity, and operational performance were compared.

RESULTS

The ID to MP-NAT relative sensitivity factors in standard dilution panels of different genotypes varied between 8.7 and 21.9 for HCV RNA, 6.7 and 14.8 for HIV RNA, and 0.71 and 11.6 for HBV DNA. Tigris was 800-fold more sensitive than cobas s 201 (1:6) for a HIV group O sample, but did not detect the HIV-2 sample picked up by cobas s 201 with equal sensitivity as the HIV-1 group M samples. The specificity of both NAT systems after initial screening of 10,520 donations with Tigris and 1444 test pools on s 201 was 99.9 percent for both systems, but reached 100 percent after the repeat and pool resolution test algorithms. A higher throughput of the pool test protocol on cobas s 201 became apparent when the daily workload was more than 400 donations.

CONCLUSIONS

Tigris ID-NAT format was significantly more sensitive than cobas s 201 MP-NAT in detecting HCV RNA and HIV RNA dilution panels, but despite the 1:6 dilution factor in s 201 the difference in sensitivity was not significant for some of the HBV genotype panels. Both NAT systems demonstrated acceptable operational performance, but for routine use further improvement in system reliability is desirable.

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

BACKGROUND

Nucleic acid testing (NAT) for hepatitis C virus (HCV) and human immunodeficiency virus (HIV) has been implemented in several European countries and in the United States, while hepatitis B virus (HBV) NAT is still being questioned by opinions both in favor and against such an option, depending on the HBV endemicity, health care resources, and expected benefits.

STUDY DESIGN AND METHODS

This survey was aimed to assess the NAT impact in improving the safety of blood supply in Italy, 6 years after implementation. The study involved 93 Italian transfusion centers and was carried out in 2001 through 2006. A total of 10,776,288 units were tested for the presence of HCV RNA, 7,932,430 for HIV RNA, and 3,405,497 for HBV DNA, respectively.

RESULTS

Twenty-seven donations or 2.5 per million tested were HCV RNA-positive/anti-HCV-negative; 14 or 1.8 per million units tested were HIV RNA-positive/anti-HIV-negative; and 197 or 57.8 per million donations tested were HBV DNA-positive/hepatitis B surface antigen-negative. Of the latter, 8 (2.3/10(6)) were collected from donors in the window phase of infection and 189 (55.5/10(6)) from donors with occult HBV. Sixty-eight percent of the latter donors had hepatitis B surface antibody, 74.5 percent of whom with concentrations considered protective (>or=10 mIU/mL).

CONCLUSION

NAT implementation has improved blood safety by reducing the risk of entering 2.5 HCV and 1.8 HIV infectious units per million donations into the blood supply. The yield of NAT in detecting infectious blood before transfusion was higher for HBV than for HCV or HIV. However, the benefit of HBV NAT in terms of avoided HBV-related morbidity and mortality in blood recipients needs to be further evaluated.

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

BACKGROUND

Blood donors in Taiwan currently are screened for hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV) infection by immunoassay. The risk of enzyme immunoassay (EIA)-negative, nucleic acid amplification technology (NAT)-reactive donations is not well understood. This study aimed to screen for such donors in Taiwan by a multiplex test (cobas TaqScreen, Roche) on a commercially available NAT system (cobas s 201 system, Roche).

STUDY DESIGN AND METHODS

NAT was performed on donors without prescreening in pools of six and NAT-reactive pools were then resolved to the single donation. Individual-donor NAT-reactive samples were discriminated by a commercially available polymerase chain reaction (PCR)-based diagnostic assay (COBAS AmpliScreen, Roche). Samples with EIA- and NAT-discordant results were investigated with supplemental serologic and confirmatory tests. Each sample taken from follow-up of HBV NAT yield cases was tested for HBV serologic profile, NAT, and viral load. The sensitivity and performance efficacy were also evaluated.

RESULTS

The 95 percent limit of detection (LOD) for HBV, HCV, and HIV were 5.09, 11.83, and 62.53 IU per mL, respectively. Among 10,727 seronegative donations, 12 HBV NAT yield cases (0.11%) and 1 HCV NAT yield case (0.01%) were detected. Follow-up results for 1 to 8 months showed that the HCV yield case was a window case and all HBV NAT yield cases were occult carriers.

CONCLUSION

The use of NAT detected occult HBV and reduced HCV window period. The yield rate, especially occult HBV, was 10- to 100-fold higher than that in developed, HBV nonendemic countries. Therefore, NAT implementation for routine donor screening in a more cost-effective manner should contribute to safer blood transfusion in Taiwan.

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.

HIV-1, HCV and HBV seronegative window reduction by the new Roche cobas® TaqScreen MPX test in seroconverting donors

BACKGROUND

By shortening the pre-seroconversion window in the viral screening of donated blood, nucleic acid amplification testing greatly improves safety and efficiency, particularly when combined with multiple target detection and maximal automation.

OBJECTIVES

Evaluation of seronegative window reduction during HIV-1, HCV and HBV infection by the novel cobas TaqScreen MPX test for simultaneous nucleic acid detection of HIV-1 (groups M and O), HIV-2, HCV and HBV using the cobas s 201 system.

STUDY DESIGN

Testing of HIV-1, HCV, and HBV seroconversion panels (20 each) using the cobas TaqScreen MPX test versus reference immuno- and nucleic acid technology assays.

RESULTS

The cobas TaqScreen MPX test detected HIV-1 and HCV infection earlier than immunoassays in 20/20 and 19/20 panels, and HBV DNA earlier than or on the same day as HBsAg in 19/20 and 18/20 panels, and later in 1 and 2 panels on neat samples and 1:6 dilutions. Pre-seroconversion sensitivity exceeded that of COBAS AmpliScreen testing in pools of 24.

CONCLUSION

The cobas TaqScreen MPX test shortens the pre-seroconversion window in minipools of six, evidencing high sensitivity, and significantly enhances blood-screening efficiency by the simultaneous automated detection of multiple viruses in a single test.

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

BACKGROUND

Screening of blood donors with nucleic acid testing (NAT) for human immunodeficiency virus (HIV) and hepatitis C virus (HCV) has been implemented recently in the United States. There are limited data, however, on the additional NAT yield of donors in developing countries in Asia where the prevalence of infection is higher. In addition, data on hepatitis B virus (HBV) NAT in high prevalence areas are minimal.

STUDY DESIGN AND METHODS

A total of 5083 whole-blood donors at the Chiang Mai University Hospital, Thailand, blood bank were evaluated with a commercially available NAT assay (Procleix Ultrio, Gen-Probe, Inc.) to screen individual donations.

RESULTS

No NAT yield cases were found for HIV-1 or HCV. There were 17 samples with discrepant HBV DNA NAT and hepatitis B surface antigen (HBsAg) tests, however. Seven of these were HBV DNA NAT-positive, HBsAg-negative; of these 7, 1 was NAT-positive at baseline, but negative on follow-up, and considered a false-positive, 1 had an acute infection, and 5 had chronic prevalent HBV infections, for a NAT yield of 6 in 4798 HBsAg negative donors (1:800). In addition there were 10 NAT-negative, HBsAg-positive serum samples. All were anti-hepatitis B core antigen immunoglobulin G-positive; on testing with a more sensitive NAT target capture assay, 5 were positive (1.8-20.6 IU/mL) and 5 were negative.

CONCLUSION

Multiplex NAT screening of individual-donor serum samples in Northern Thailand detected approximately 1 per 800 HBV NAT-positive, HBsAg-negative donors. The especially high prevalence of HBV infection in Thailand and other Asian countries suggests that HBV NAT screening of donors will be more cost-effective than in other areas.

Current risks of transfusion-transmitted agents: a review

CONTEXT

Infectious disease testing has dramatically improved the safety of blood for transfusion in the United States, especially since the introduction in 1999 of nucleic acid amplification testing. In 2004, methods (primarily culturing) for detecting bacteria in platelets were also added.

OBJECTIVE

To provide current risk estimates for the likelihood of viral transmission by test-negative blood components and to illustrate the safety improvements since the introduction of bacterial testing of platelets.

DATA SOURCES

Published literature from 1999 through 2006 and unpublished American Red Cross data sources.

CONCLUSIONS

The risk of human immunodeficiency virus and hepatitis C virus transmission through blood transfusion since the introduction of nucleic acid amplification testing is approximately 1 in 2 million. Hepatitis B virus risk, for which nucleic acid amplification testing is not performed routinely, remains at 1 in 200,000 to 500,000 using a combination of anti-hepatitis B core and hepatitis B surface antigen testing. Seven cases of transfusion-transmitted West Nile virus have been reported since the introduction of nucleic acid amplification testing in 2003, but none has been reported since system-wide implementation of processes to increase the test sensitivity for use in epidemic areas. The residual risk of receiving a bacterially contaminated platelet component with clinical consequences is estimated at approximately 1 in 75,000, if culture negative and 1 in 33,000 if not tested by culture methods.

[Future technological evolutions in blood donation qualification]

In the past decades, blood donation screening contributed significantly to blood safety improvement, thanks to the increasing performances of serological and nucleic acid testing (NAT) assays, as well as the evolution of automated systems technology. The rapid pace of NAT development can be clearly seen to extend into the future. NAT for additional viruses as well as the use of new automated systems for individual donation or smaller mini-pool testing, with multiplex assays, is currently debated. However, few added benefit is expected for blood safety from such developments, while cost-effectiveness appears to be poor. The next step in laboratory automation will probably be the implementation of robotic pre- and post-analytical procedures. In this article we review the potential future evolutions of screening technologies in blood qualification platforms, particularly those derived from nanobiotechnologies. DNA microarrays, Lab-On-Chips, biosensors and nanoparticles (quantum dots) will probably play a major role in the coming decade.

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.

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.

Analytical and clinical sensitivity of the Procleix Ultrio HIV-1/HCV/HBV assay in samples with a low viral load

BACKGROUND AND OBJECTIVES

The Procleix Ultrio human immunodeficiency virus type 1 (HIV-1)/hepatitis C virus (HCV)/hepatitis B virus (HBV) (Ultrio) assay simultaneously detects HIV-1 RNA, HCV RNA and HBV DNA in individual blood donations. The main objective of the study was to assess the analytical and clinical sensitivity of the multiplex and discriminatory probe assays in samples with a low viral load.

MATERIAL AND METHODS

The VQC HIV RNA genotype B, HCV RNA genotype 1 and HBV DNA genotype A standard dilutions were tested in 26 repeats. The probability of detection by Ultrio was compared with previously obtained data of the Procleix Duplex HIV-1/HCV assay on the same reference panels. A selection of 121 anti-HIV-1, 138 anti-HCV and 190 HBsAg positive samples from patients receiving antiviral therapy were tested. The majority of patient samples had a viral load below the detection limit of the diagnostic nucleic acid test assays, which made them suitable to evaluate the performance of the multiplex and discriminatory assays on yield cases with a similar low viral load.

RESULTS

The 95% and 50% detection end-points of the Ultrio assay along with the corresponding 95% confidence intervals are 53.7 (32.9-117.2) and 8.6 (6.2-12.1) geq/ml for HIV-1 RNA, 30.3 (19.0-62.4) and 5.2 (3.7-7.2) geq/ml for HCV RNA and 393.7 (147.9-6978) and 54.5 (22.4-143.8) geq/ml for HBV DNA. The analytical sensitivity of Ultrio expressed as a potency factor relative to previously obtained Duplex results on the same HIV-1 RNA and HCV-RNA standard dilutions was 1.09 (0.20-6.10) and 1.11 (0.21-5.89), respectively. The assay detected all 22 HIV-1 infected patients with viral load > 50 copies/ml, and 41 of 99 patients (41%) with viral load < 50 copies/ml, of which 23 (56%) were detected by the discriminatory assay. All 47 patients with HCV RNA load > 521 IU/ml and 10/91 polymerase chain reaction-negative patients with viral load < 50 IU/ml tested positive in Ultrio assay of which five were missed in the discriminatory test. The assay detected 53/55 HBV infected patients (96%) with viral load > 250 copies/ml and 108/135 patients (80%) with viral load < 250 copies/ml of which 17 (16%) were missed by the discriminatory test.

CONCLUSIONS

The new Procleix Ultrio assay is as sensitive as the Procleix Duplex assay for HIV-1 and HCV detection meeting the requirements of universal guidelines. The ability of the assay to detect HBV DNA in low viral load samples could be useful for screening blood. Inevitable negative results of discriminatory probe assays caused by stochastic sample variation will reduce the chance of recognizing low viraemic blood donors detected by individual donation nucleic acid test.

Characterization of HBV DNA+/HBsAg- blood donors in Poland identified by triplex NAT

Nucleic acid testing (NAT) for hepatitis B virus (HBV) has been performed in Poland since 2005 on samples seronegative for hepatitis B surface antigen (HBsAg), anti-hepatitis C virus (anti-HCV), and anti-human immunodeficiency virus (anti-HIV). Tools included 24-donation pool testing (PT) using Cobas Amplicor or in individual donations (ID) by Procleix Ultrio. Seven of 761,666 (1:108,800) and 21/250,191 (1:11,900) HBV DNA-positive donations were identified and confirmed by alternative methods. HBV DNA load ranged between 11.6 and 4.6 x 10(4) IU/mL in 11 samples and could not be quantified in 17 samples. HBV genotypes A (56%) and D (4%) were found. The analysis of combined results from index, follow-up, and look-back samples identified four groups: (1) Two cases tested HBsAg positive with alternative, more sensitive, assays; (2) Four cases were in the pre-seroconversion window period; (3) Eight cases had a fluctuating pattern of HBV DNA and anti-HBs detection (recovered infection); and (4) twelve cases carried anti-HBc without anti-HBs, which might correspond to either chronic or recovered "occult" HBV infection. One donor with no HBV markers in the follow-up was excluded, and another was in the window period preceding anti-HBs. HBV NAT identified more confirmed positive donors than HCV or HIV NAT, and 1:250,000 could not be detected by anti-HBc screening. Serological and molecular studies on follow-up and look-back samples are important to classify donors. In conclusion, further studies are needed to determine whether the considerably higher yield of HBV DNA detection obtained with individual donation screening improves blood safety compared with anti-HBc screening.

Quantification of hepatitis B virus genomes and infectivity in human serum samples

BACKGROUND

Hepatitis B virus (HBV) infections are still a major health issue, with approximately 350 million people chronically infected with HBV worldwide. Information about the minimum copy number of HBV genomes required for infection would be useful as a reference for drug and vaccine development; for monitoring HBV patients during treatment; for screening of blood, organ, and tissue donors; and for regulating nucleic acid amplification assays for HBV.

STUDY DESIGN AND METHODS

Serum samples from chronic carriers (hepatitis B surface antigen-positive and antibody to HBV core antigen-positive) of the three most common subtypes of HBV were studied; their infectivity titers had been evaluated previously in chimpanzees. The genotypes of the HBV samples were determined by DNA sequences and type-specific amino acids of the S gene of HBV. Copy numbers of HBV DNA were quantified by real-time TaqMan polymerase chain reaction (PCR) and by nested PCR applied to limiting dilutions. The copy number determined for each inoculum was compared with previously defined chimpanzee infectivity titers.

RESULTS

The genotypes of the HBV adw, ayw, and adr inocula were A, D, and C, respectively. The concentration of HBV DNA was determined to be 5.4 x 10(9), 2.5 x 10(9), and 3.1 x 10(8) genome equivalents (geq) per mL for serum samples containing the adw, ayw, and adr, respectively. The chimpanzee infectivity titers per milliliter of these initial HBV-containing serum samples were previously determined to be 10(7.5) for adw, 10(7.5) for ayw (MS-2 strain), and 10(8) for adr.

CONCLUSION

The minimal copy number of HBV DNA in chronic carriers of HBV that can infect the chimpanzee model was estimated to be from 3 to 169 geq based upon the three well-characterized inocula.

Anti-HBc screening of blood donors: a comparison of nine anti-HBc tests

BACKGROUND AND OBJECTIVES

Since voluntary introduction of hepatitis B virus (HBV) minipool nucleic acid amplification technology (NAT) at the German Red Cross, the expected residual risk of a transfusion-associated HBV infection has been estimated to be 1 : 500,000 - about 10 times higher than for human immunodeficiency virus (HIV) or hepatitis C virus (HCV) infection. Donors demonstrating chronic positivity for antibody to hepatitis B core antigen (anti-HBc), negativity for hepatitis B surface antigen (HBsAg) and polymerase chain reaction (PCR)-negative with a low virus load are a major cause of this increased risk.

MATERIALS AND METHODS

Ten-thousand blood donors from our blood-donation centre were screened for anti-HBc using the current PRISM HBc and the new PRISM HBcore assay to evaluate the diagnostic sensitivity and specificity of these tests. PRISM HBc- or PRISM HBcore-reactive samples were further analysed using seven additional tests for anti-HBc, two tests for antibody to hepatitis B surface antigen (anti-HBs), one test for antibody to hepatitis B envelope antigen (anti-HBe) and three HBV NAT assays.

RESULTS

From a total of 10,000 donors, nine and 14 samples were reactive only in the PRISM HBc and the PRISM HBcore, respectively, whereas 165 samples were reactive in both anti-HBc assays. Further analysis of these 188 anti-HBc-reactive specimens in a total of nine different anti-HBc assays revealed concordant results for 162 (86.2%) specimens. Sample cut-off values for anti-HBc were significantly (P < 0.01) lower for anti-HBc-only reactive samples compared with specimens that were also reactive for anti-HBs or anti-HBe.

CONCLUSIONS

Both PRISM anti-HBc assays revealed that approximately 1.8% of non-prescreened blood donors from Germany were reactive for anti-HBc. Although sensitivity was comparable between both assays, specificity was increased significantly with the PRISM HBcore. High anti-HBc sample cut-off values were indicative for reactivity in other HBV parameters and for concordant results in the nine different anti-HBc assays. Look-back investigations are necessary to estimate the infection risk both of anti-HBc-only positive and of anti-HBc/anti-HBs-positive blood transfusions.

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.

Acute hepatitis B virus window-period blood donations detected by individual-donation nucleic acid testing: a report on the first two cases found and interdicted in Spain

BACKGROUND

Mathematical models predict that, in Spain, a significant number of blood units will be obtained during the window period of the hepatitis B virus (HBV) infection. Routine nucleic acid testing (NAT) on individual blood units may provide experimental data to evaluate such a theoretical risk.

STUDY DESIGN AND METHODS

Between February and July 2005, a total of 34,631 individual units were screened for HBV DNA by a multiplex transcription-mediated amplification (TMA) test. Units that repeatedly reacted in the test, but did not react for HBV surface antigen (HBsAg), were submitted to additional testing by both molecular and conventional assays, and the donors were recalled for follow-up studies and the collection of clinical and epidemiologic data.

RESULTS

Confirmatory testing and follow-up studies identified 2 blood units donated during the HBV infection window period (1/17,316 units studied). Sequencing of amplification products obtained by nested polymerase chain reaction (n-PCR) revealed two HBV strains from genotypes D/ayw3 and F/adw4q-, but did not identify HBsAg mutants. The HBV DNA concentration in the index donations was estimated to be below the n-PCR detection level (180 IU/mL), in both cases. One donor developed acute hepatitis 2 months after donating blood, but the other remained asymptomatic and displayed normal alanine aminotransferase levels at follow-up.

CONCLUSIONS

The HBV infection window period is a real issue in the setting of Spanish blood transfusions. NAT of individual units by TMA would make a significant contribution to improving the safety of the blood supply in Spain. Additional studies involving a larger number of units and longer periods of time are required, however, to ascertain the true incidence of the problem in this country.

Changing patterns of hepatitis B infection in Italy and NAT testing for improving the safety of blood supply

In Italy, as in most industrialized countries, the burden of hepatitis B has progressively declined in recent decades as a consequence of general improvements in hygiene and standard of living, the introduction of several public health measures, refinement in blood screening and the implementation of specific vaccination programmes. Universal hepatitis B vaccination for all infants and adolescents as well as individuals at increased risk has resulted in considerable progress towards prevention and control of HBV infection. The residual risk of transmitting blood-borne viruses through transfusion is currently very low. Nucleic acid testing can shorten the window period and, consequently, further reduce the risk of viral transmission. Blood donor screening for HCV by NAT was initiated in Italy in 2001 and became mandatory in June 2002. NAT for HIV is currently mandatory in four regions, not mandatory but almost universally performed in another thirteen regions, and not yet introduced in the remaining four regions. NAT for HBV is currently mandatory in four regions and under evaluation in the remaining. NAT for HBV may be a useful tool in detecting acute viral infections in the window phase as well as the occult infections. Its efficacy in improving the safety of blood supply is expected to be higher in countries with intermediate/high endemicity, where anti-HBc antibody screening cannot be routinely performed. There is agreement that, at present, the implementation of HBV DNA testing will not allow for discontinuation of screening for HBsAg.

Evaluation of a new molecular assay for detection of human immunodeficiency virus type 1 RNA, hepatitis C virus RNA, and hepatitis B virus DNA

BACKGROUND

Rapid, sensitive, specific, and cost-effective screening of donated blood to prevent transmission of infectious agents remains challenging. In recent years, incorporation of nucleic acid testing for HIV-1 and HCV RNA improved blood safety by reducing the window period between infection and serologic detection. For HBV infection, this window period with most serologic assays is 50-60 days. Adding a nucleic acid test (NAT) for HBV DNA with existing NATs for HIV-1 and HCV RNA would further improve blood safety and blood screening efficiency.

OBJECTIVE

To evaluate the Procleix Ultrio Assay for simultaneous detection of HIV-1 and HCV RNA and HBV DNA and corresponding discriminatory assays.

STUDY DESIGN

The performance of these assays, which utilize the same technology and assay format as the Procleix HIV-1/HCV assay, was determined using relevant clinical specimens and analytical sensitivity and specificity panels.

RESULTS

The Procleix Ultrio Assay demonstrated specificity of > or =99.5% in healthy donor blood specimens and in plasma containing potentially interfering substances or other blood-borne pathogens. Assay sensitivity demonstrated >95% detection of 100copies/mL, 30IU/mL, and 15IU/mL for HIV-1 and HCV RNA, and HBV DNA, respectively. The assay detects all known HIV-1 subtypes and HCV and HBV genotypes and is highly reproducible. Statistical analysis using receiver operating characteristic plots demonstrated wide analyte cutoff values for each assay associated with assay specificity and sensitivity of > or =99.5%.

CONCLUSIONS

In this investigational study, the Procleix Ultrio Assay sensitivity and specificity were similar to existing NATs used in blood-bank settings to detect HIV-1 and HCV RNA and provided equivalent sensitivity and specificity for detection of HBV DNA. Using this combination assay, blood safety may be improved and the multiplex format enhances blood screening efficiency. The throughput capability of this assay is compatible with large volume processing and the chemistry is adaptable to full automation.

Evaluation of COBAS AmpliPrep nucleic acid extraction in conjunction with COBAS AmpliScreen HBV DNA, HCV RNA and HIV-1 RNA amplification and detection

BACKGROUND AND OBJECTIVES

This report describes the evaluation of the COBAS AmpliPrep instrument for fully automated generic nucleic acid extraction in conjunction with hepatitis B virus (HBV) DNA, hepatitis C virus (HCV) RNA, and human immunodeficiency virus (HIV)-1 RNA COBAS AmpliScreen amplification and detection using serial dilutions of the WHO international standards (IS) and the PeliCheck reference panels.

MATERIALS AND METHODS

Serial diluted samples of the WHO IS and the PeliCheck reference panels were tested 24 times to determine the HBV DNA, HCV RNA and HIV-1 RNA detection limits by Probit analysis. The existence and extent of cross-contamination were assessed by testing alternating high titre HBV DNA-positive and -negative samples. The specificity of the AmpliPrep-AmpliScreen test for HBV was determined by testing 232 minipools consisting of six donations, all negative for HCV/HIV-1 nucleic acid testing (NAT) and HBsAg. In addition, a HBV genotypes A-G panel was tested.

RESULTS

The respective 95% detection limits (and 95% CI) on the WHO IS and on the PeliCheck reference panels were 6.7 (4.3-13) IU/ml and 123 (68-301) gEq/ml for HBV DNA, 23 (11-106) IU/ml and 126 (84-233) gEq/ml for HCV RNA, and 187 (108-422) IU/ml and 183 (108-434) gEq/ml for HIV-1 RNA. Based on the WHO IS and the PeliCheck reference panels, no significant differences in sensitivity for HBV and HCV were found between AmpliPrep and the licensed MultiPrep extraction method. The sensitivity of AmpliPrep-AmpliScreen for HIV-1 was probably twofold lower as compared to the MultiPrep-AmpliScreen method. No cross contamination was observed. All 232 minipools were HBV NAT-negative. The AmpliPrep-AmpliScreen test for HBV detected HBV genotypes A-G with equal sensitivity.

CONCLUSIONS

The AmpliPrep instrument combined with the AmpliScreen assays for HBV, HCV and HIV-1 is robust and suitable for NAT donor screening. The sensitivity criteria for HIV-1 and HCV as defined by the Paul Ehrlich Institute and the Food and Drug Administration for minipool NAT screening are met by this system. SINGLE SENTENCE SUMMARY: Generic COBAS AmpliPrep nucleic acid extraction in conjunction with COBAS AmpliScreen detection for HBV, HCV and HIV-1.