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High Throughput Donor Plasma NAT Screening Assay Applied to Acute HIV Detection in a Public
Health Setting
December 5, 2007
Josh Goldsmith, Ph.D.National Genetics Institute, a LabCorp Company
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Presentation Outline Current challenges with acute HIV screening NGI PCR and pooling methods A prospective clinical study to validate the
method for plasma donor screening Acute HIV demonstration project with SFDPH
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Challenges in the Implementation of PCR-Based Acute HIV Screening Programs Availability of validated methods Availability of “off-the-shelf” methods Availability of cost-effective methods Availability of scalable methods where broad-
based screening programs are envisioned
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National Genetics Institute (NGI) Profile A provider of automated, sensitive PCR methods for infectious
disease testing Offers assays for HIV, HAV, HBV, HCV, and other infectious
agents Screens the majority of US supply of source plasma for infectious
agents (~8M donations/year) with pools of 512 samples A licensed clinical laboratory and approved by FDA CBER to
perform pooled nucleic acid testing for donor plasma screening A subsidiary of LabCorp with access to blood draw centers and
courier networks throughout the US
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Dilution Profile
Analytical Sensitivity of UltraQual HIV-1 PCR
Probit Analysis
99% detection cut-off = 5
copies/ml
512 x 5 copies/ml
= 2560 copies/ml
(minimum titer in individual sample to have
99% probability of detection in 512 sample pool
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NGI Pooling and Pool Resolution Process Launch Executable File
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NGI Prospective Clinical StudyStudy Objectives
To demonstrate HIV-1 PCR testing of pooled plasma samples can accurately detect HIV-1 infection
To validate plasma pooling and pool resolution process for pools ≤ 512 individual samples
To determine the clinical sensitivity and specificity of the pooling and pool resolution process
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NGI Prospective Clinical StudyStudy Design
342,729 plasma donations collected from ~48,000 donors donating at 33 donor centers over a 3.5 months
Informed consent obtained for HIV Ab and RT-PCR testing
Individual plasma samples tested for HIV Ab (Bio-Rad) and HIV-1 p24 antigen (Coulter) and HIV RNA (NGI)
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NGI Prospective Clinical StudyPool Numbers and Sizes
Summary of Master Pools and Donations Tested During Clinical Study Period
Master pools Donations
n (%) n (%) Min Max Mean SD
Tested during study 703 (100.00) 345,320 (100.00) 233 510 491 17
No results 6 ( 0.85) 2,591 ( 0.75) 233 509 432 110
Analyzed for study 697 ( 99.15) 342,729 ( 99.25) 388 510 492 14
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NGI Prospective Clinical Study Results
Rate of HIV-1 RT-PCR Positivity Found in Plasma Donations by Master Pool Testing and the Resolution Testing Algorithm
HIV RT-PCR positive
N N %
All donations in clinical trial 342,729 18 0.0053
Donations from repeat donors 316,099 15 0.0047
Donations from new donors 26,630 3
HIV-1 Ab negative donations 342,684 10 0.0029
Donations from repeat donors 316,065 10 0.0031
Donations from new donors 26,619 0
HIV-1 Ab negative, p24 Ag negative donations
342,674 6 0.0018
Donations from repeat donors 316,055 6 0.0019
Donations from new donors 26,619 0
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NGI Prospective Clinical Study ResultsClinical Specificity-false positives
samples HIV-1 PCR (-)Clinical Specificity = samples HIV-1 (-)*
* HIV-1 (-) defined as samples for which test results for HIV-1 PCR,
HIV EIA, and/or p24 antigen are negative
342,668 HIV-1 PCR (-)Clinical Specificity = 342,668 HIV-1 (-)* (HIV-1 PCR)
= 100%**
**95% CI 99.6-100%
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NGI Prospective Clinical Study ResultsClinical Sensitivity-false negatives
samples HIV-1 PCR (+)Clinical Sensitivity =
samples HIV-1 (+)*
* HIV-1 (+) defined as subjects for which test results for HIV-1
PCR, HIV EIA, and/or p24 antigen are positive
18 HIV-1 PCR (+)Clinical Sensitivity = (HIV-1 PCR) 18 HIV-1 (+)*
= 100%**
**95% CI 83.3-100%
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NGI Prospective Clinical StudyStudy Conclusions HIV-1 PCR testing of pooled plasma samples
can accurately detect HIV-1 infection Plasma pooling and pool resolution process for
pools ≤ 512 individual samples is validated Clinical sensitivity and specificity of the pooling
and pool resolution process is high NGI received FDA biologics license from FDA (CBER) for screening of donated plasma based
on the study results
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San Francisco Department of Public Health (SFDPH) Demonstration Project - Study Overview
Patient samples were collected from the SFDPH city clinics and community based services over a 5-month period
Samples were screened by SFDPH for HIV antibodies with standard EIA (Vironostika) or rapid HIV antibody tests (Orasure Technologies)
HIV Ab (-) samples were picked up by LabCorp couriers and transported to NGI for testing
NAT positive samples were identified in pools of 64 samples and confirmed by individual NAT
All patients identified as positive were counseled and referred for HIV care and follow-up by SFDPH.
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San Francisco Department of Public Health (SFDPH) Demonstration ProjectStudy Results
NAT testing identified 5 additional HIV-positive samples increasing the
overall HIV detection rate by 12% to 3.1%.
Total Positive (+) Negative (-) Positivity Rate
Patient Samples Collected 1536
HIV Ab Testing 1536 43 1493 2.8%
HIV NAT Testing 1444 5 1439 0.3%
HIV Ab and NAT Testing 1536 48 3.1%
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Conclusions A pooled specimen HIV PCR assay has been validated for large-
scale plasma donor screening involving pools of up to 512 samples
The method was applied to the detection of acute HIV in a public health setting with SFDPH
As this method is routinely used for screening millions of blood plasma donations per year, opportunities exist to implement broad-based acute HIV screening programs in a highly cost-effective fashion
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Acknowledgements
San Francisco Department of Public Health
Jeff Klausner MD, MPH
Nicola Zetola, Ph.D.
Katherine Ahrens, MPH
National Genetics Institute/LabCorp
Mark Richardson, CLSpMB Richard Smith, Ph.D.
Hawazin Faruki, Ph.D.