Relative Sensitivities of US Licensed NAT Assays for Detection of Viremia in Early HIV and HCV Infection

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 gt1 PCR(), Ab(-) gt2 PCR(-),
Ab(-) gt2 wk pre-quantification lt7 days between
samples
Discrepancies ?
SuperQuant TM RT PCR X 1
RNA Quantifiable Samples
Non-Quantifiable Samples (lt100 copies/mL)
NO
YES
12 Panels 116 Serial Samples
END
Ultra Qual RT PCR X 5-10
lt5000 copies / mL
gt5000 copies / mL
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 gt1 PCR(), Ab(-) gt2 PCR(-),
Ab(-) gt 2 wks pre-quantification lt7 days
between samples
Discrepancies ?
COBAS Amplicor HCV Monitor v2.0 PCR X 1
RNA Quantifiable Samples
Non-Quantifiable Samples lt1,620 copies/mL
NO
YES
12 Panels 180 Serial Samples
END
d-HCV TMA X 4
lt5000 copies / mL
gt5000 copies / mL
Neat MP x 1
Neat MP x 3
20 add'l replicates for a given assay and
dilution.
5
Discrepancies
Samples Discrepancies () Quantifiable Discrepancies
HIV HCV 113 180 26 (23) 31 (17) 8 (100-340 copies/mL) 1 (3,600 copies/mL)
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Representative Discrepancies between G-P TMA and
Roche PCR on HIV Panels
Discrepancy between Neat HIV-HCV TMA and Neat HIV PCR Discrepancy between Neat HIV-HCV TMA and Neat HIV PCR Discrepancy between Neat HIV-HCV TMA and Neat HIV PCR Discrepancy between Neat HIV-HCV TMA and Neat HIV PCR Discrepancy between Neat HIV-HCV TMA and Neat HIV PCR
Sample RNA Copies / mL HIV-HCV TMA Neat No. Reactive / No. Replicates HIV PCR Neat No. Reactive / No. Replicates
1 lt 100 12 / 23 4 / 23
2 lt 100 1 / 23 0 / 3
3 lt 100 2 / 23 3 / 22
4 lt 100 3 / 23 2 / 23
5 lt 100 2 / 23 1 / 23
6 lt 100 1 / 23 0 / 23
7 lt 100 4 / 23 3 / 22
8 lt 100 18 / 23 3 / 3
9 lt 100 5 / 23 12 / 23
10 lt 100 5 / 23 0 / 23
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Representative Discrepancies between G-P TMA and
Roche PCR on HIV Panels
Discrepancy between 116 MP HIV-HCV TMA and 124 MP HIV PCR Discrepancy between 116 MP HIV-HCV TMA and 124 MP HIV PCR Discrepancy between 116 MP HIV-HCV TMA and 124 MP HIV PCR Discrepancy between 116 MP HIV-HCV TMA and 124 MP HIV PCR Discrepancy between 116 MP HIV-HCV TMA and 124 MP HIV PCR
Sample RNA Copies / mL HIV-HCV TMA 116 No. Reactive / No. Replicates HIV PCR 124 No. Reactive / No. Replicates

1 lt 100 5 / 23 4 / 23
2 lt 100 6 / 23 7 / 22
3 lt 100 12 / 23 7 / 23
4 lt 100 0 / 23 2 / 22
5 100 22 / 23 18 / 23
6 100 9 / 23 8 / 23
7 100 9 / 23 3 / 22
8 200 7 / 23 8 / 21
9 300 16 / 23 9 / 23
10 340 18 / 23 22 / 22
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Odds Ratios (OR) and 95 CIs Comparing Assays
Performed Neat or in Mini-Pools (MP)
HIV OR (95 CI) HCV OR (95 CI)
116 MP HIV-HCV TMA vs. 124 MP PCR 1.8 (1.3 - 2.5) 4.0 (2.8 - 5.8)
Neat HIV-HCV TMA vs. Neat PCR 1.0 (0.72 - 1.4) 2.3 (1.6 - 3.2)
HIV-HCV TMA vs. d-TMA 1.2 (0.72 - 2.1) 1.2 (0.76 - 1.8)
Neat vs. 116 MP (HIV-HCV TMA) 45.3 (20.9 - 97.9) 52.3 (23.5 - 116.6)
Neat vs. 124 MP (PCR) 79.1 (32.7 - 191.5) 93.4 (37.3 - 233.8)
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Differential WP (?WP ) 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 HIV HCV HCV
?WP (95 CI) ? Yield (95 CI) ?WP (95 CI) ? Yield (95 CI)
116 MP HIV-HCV TMA vs. 124 MP PCR 0.5 (0.2, 0.8) 0.3 (0.1, 0.5) 0.6 (0.4, 0.8) 0.5 (0.3, 0.7)
Neat HIV-HCV TMA vs. Neat PCR 0.0 (-0.3, 0.3) 0.0 (-0.2, 0.2) 0.4 (0.2, 0.6) 0.3 (0.1, 0.4)
HIV-HCV TMA vs. d-TMA 0.2 (-0.3, 0.7) 0.1 (-0.2, 0.4) 0.1 (-0.1, 0.3) 0.1 (-0.1, 0.2)
Neat vs. 116 MP (HIV-HCV TMA) 3.4 (3.0, 3.8) 2.0 (1.5, 2.6) 1.8 (1.6, 2.0) 1.4 (1.1, 1.7)
Neat vs. 124 MP (PCR) 3.9 (3.4, 4.4) 2.3 (1.7, 2.9) 2.1 (1.9, 2.3) 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.
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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