Background and Rationale

1. Relative Sensitivities of US Licensed NAT Assays for Detection of Viremia in Early HIV and HCV Infection MP Busch, SA Glynn, DJ Wright, D Hirschkorn, ME Laycock, JD McAuley, Y Tu, C Giachetti, J Gallarda, J Heitman, S Kleinman NHLBI-REDS NAT Study Group (submitted to Transfusion)

2. Background and Rationale • Two licensed NAT Systems in US • Roche Ampliscreen (Multi/Std-Prep / PCR) • Gen-Probe/Chiron Procleix (TC / TMA) • Manufacturer licensure trials and previous blood industry studies have documented analytical sensitivities and WP closure relative to serology • Comparable clinical yields (NAT-only donations) in US screening (Stramer et al. NEJM 2004), but limited power to detect differences • No previous head-to-head study of performance on SC panels in ID- and MP-NAT contexts

3. HIV Panel Testing Algorithm 44 HIV Panels 145 Serial Samples Sample Selection >1 PCR(+), Ab(-) >2 PCR(-), Ab(-) >2 wk pre-quantification <7 days between samples Discrepancies ? SuperQuant [TM] RT PCR X 1 RNA Quantifiable Samples Non-Quantifiable Samples (<100 copies/mL) YES NO 12 Panels 116 Serial Samples END >5000 copies / mL <5000 copies / mL Ultra Qual RT PCR X 5-10 Neat & MP x1 Neat & MP x 3 20 add'l replicates for a given assay and dilution.

4. HCV Panel Testing Algorithm 55 HCV Panels 629 Serial Samples Sample Selection >1 PCR(+), Ab(-) >2 PCR(-), Ab(-) > 2 wks pre-quantification <7 days between samples Discrepancies ? COBAS Amplicor HCV Monitor v2.0 PCR X 1 RNA Quantifiable Samples Non-Quantifiable Samples <1,620 copies/mL YES NO 12 Panels 180 Serial Samples END >5000 copies / mL <5000 copies / mL d-HCV TMA X 4 Neat & MP x 1 Neat & MP x 3 20 add'l replicates for a given assay and dilution.

5. Discrepancies

6. Representative Discrepancies between G-P TMA and Roche PCR on HIV Panels

7. Representative Discrepancies between G-P TMA and Roche PCR on HIV Panels

8. Odds Ratios (OR) and 95% CIs Comparing Assays Performed Neat or in Mini-Pools (MP)

9. Differential WP (ΔWP *) in Days and Differential Yields of Viremic Donations per 10,000,000 Donations ‡ (95% CI) for Comparisons of NAT Assays Performed Neat or on Mini-Pool (MP) Dilutions * based on doubling times: HIV, 20.5 hrs; HCV, 10.8 hrs. ‡ based on US incidence rates: HIV, 2.16 per 100,000 person-years; HCV, 2.80 per 100,000 person-years.

10. Conclusions • Findings reassuring with respect to comparability of licensed NAT systems • Differences in MP-NAT sensitivity translated into extremely small window period and yield differences • 12 and 14 hours for HIV and HCV, respectively • 1 infected donation per 20 million (HCV) or 33 million (HIV) units • Support Stramer et al. (NEJM 2004) finding of similar HIV and HCV MP-NAT yields for Gen-Probe/Chiron and Roche NAT users • Differences in sensitivity of ID- vs MP-NAT consistent with previous estimates based on viral doubling time models • 2 to 4 day WP closure and 1 to 2 ID-only yield cases per 10 million units for HIV and HCV, respectively • Data supports accuracy of dTMA and PCR for resolution of reactive MPs, and for “cross-supplemental” testing for counselling/reinstatement