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)
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
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 X1
RNA Quantifiable Samples
Non-Quantifiable Samples (<100 copies/mL)
YES 12 Panels 116 Serial Samples
NO
END Ultra Qual RT PCR X 5-10 >5000 copies / mL <5000 copies / mL
Neat & MP x1
Neat & MP x 3
20 add'l replicates for a given assay and dilution.
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 12 Panels 180 Serial Samples
NO
END d-HCV TMA X 4 >5000 copies / mL Neat & MP x 1 <5000 copies / mL Neat & MP x 3
20 add'l replicates for a given assay and dilution.
Discrepancies
# Samples # Discrepancies (%)
HIV HCV 113 180 26 (23%) 31 (17%)
# Quantifiable Discrepancies
8 (100-340 copies/mL) 1 (3,600 copies/mL)
Representative Discrepancies between G-P TMA and Roche PCR on HIV Panels
Discrepancy between Neat HIV-HCV TMA and Neat HIV PCR Sample RNA Copies / mL HIV-HCV TMA Neat No. Reactive / No. Replicates 12 / 23 1 / 23 HIV PCR Neat No. Reactive / No. Replicates 4 / 23 0/3
1 2
< 100 < 100
3
4 5 6 7 8 9 10
< 100
< 100 < 100 < 100 < 100 < 100 < 100 < 100
2 / 23
3 / 23 2 / 23 1 / 23 4 / 23 18 / 23 5 / 23 5 / 23
3 / 22
2 / 23 1 / 23 0 / 23 3 / 22 3/3 12 / 23 0 / 23
Representative Discrepancies between G-P TMA and Roche PCR on HIV Panels
Discrepancy between 1:16 MP HIV-HCV TMA and 1:24 MP HIV PCR Sample RNA Copies / mL HIV-HCV TMA 1:16 No. Reactive / No. Replicates HIV PCR 1:24 No. Reactive / No. Replicates
1 2 3 4 5 6 7 8 9 10
< 100 < 100 < 100 < 100 100 100 100 200 300 340
5 / 23 6 / 23 12 / 23 0 / 23 22 / 23 9 / 23 9 / 23 7 / 23 16 / 23 18 / 23
4 / 23 7 / 22 7 / 23 2 / 22 18 / 23 8 / 23 3 / 22 8 / 21 9 / 23 22 / 22
Odds Ratios (OR) and 95% CIs Comparing Assays Performed Neat or in Mini-Pools (MP)
HIV OR (95% CI) 1:16 MP HIV-HCV TMA vs. 1:24 MP PCR Neat HIV-HCV TMA vs. Neat PCR HIV-HCV TMA vs. d-TMA Neat vs. 1:16 MP (HIV-HCV TMA) Neat vs. 1:24 MP (PCR) 1.8 (1.3 - 2.5) 1.0 (0.72 - 1.4) 1.2 (0.72 - 2.1) 45.3 (20.9 - 97.9) 79.1 (32.7 - 191.5) HCV OR (95% CI) 4.0 (2.8 - 5.8) 2.3 (1.6 - 3.2) 1.2 (0.76 - 1.8) 52.3 (23.5 - 116.6) 93.4 (37.3 - 233.8)
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
HIV
ΔWP (95% CI) Δ Yield (95% CI)
HCV
ΔWP (95% CI) Δ Yield (95% CI)
1:16 MP HIV-HCV TMA vs. 1:24 MP PCR Neat HIV-HCV TMA vs. Neat PCR
0.5 (0.2, 0.8) 0.0 (-0.3, 0.3)
0.3 (0.1, 0.5) 0.0 (-0.2, 0.2)
0.6 (0.4, 0.8) 0.4 (0.2, 0.6)
0.5 (0.3, 0.7) 0.3 (0.1, 0.4)
HIV-HCV TMA vs. d-TMA Neat vs. 1:16 MP (HIV-HCV TMA)
Neat vs. 1:24 MP (PCR)
0.2 (-0.3, 0.7) 3.4 (3.0, 3.8)
3.9 (3.4, 4.4)
0.1 (-0.2, 0.4) 2.0 (1.5, 2.6)
2.3 (1.7, 2.9)
0.1 (-0.1, 0.3) 1.8 (1.6, 2.0)
2.1 (1.9, 2.3)
0.1 (-0.1, 0.2) 1.4 (1.1, 1.7)
1.6 (1.2, 2.0)
* 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.
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 “crosssupplemental” testing for counselling/reinstatement