CDC HIV Diagnostics Conference December 5 7 2007
CDC HIV Diagnostics Conference December 5 -7, 2007 Sensitivity of Ora. Quick and Early Generation Enzyme Immunoassay (EIA) within a Pooled HIV Nucleic Acid Amplification Testing (HIV NAAT) Program J Stekler 1, 2, PD Swenson 2, RW Coombs 1, J Dragavon 1, RW Wood 1, 2, MR Golden 1, 2 From the 1 University of Washington, Seattle, WA and 2 Public Health - Seattle & King County (PHSKC), WA
Objective ●To describe the sensitivity of different HIV antibody tests within an HIV NAAT program ● To understand that HIV test sensitivity may vary in populations with different rates of HIV acquisition and testing intervals
Background ● 9/2003: pooled NAAT testing began ● Targeted HIV NAAT: men who have sex with men (MSM) prevalence = 16% incidence = 2. 7 per 100 person-years ● Sites: rapid Ab testing: CBO, bathhouses, or high-risk at STD 1) UAI w/ HIV-positive or unknown serostatus partner, 2) bacterial STD, or 3) methamphetamine/popper use in last year standard Ab testing (EIA): mostly “low-risk” STD clients
Methods: HIV testing ● Rapid testing Ora. Quick (Orasure Technologies, Inc) fingerstick whole blood or oral fluids ● EIA Vironostika HIV-1 Microelisa System (Organon Teknika Corp) Genetic Systems r. LAV EIA (Bio-Rad Laboratories) ● HIV NAAT: 30 person pools (manually combined) 9/03 -1/05: Procleix HIV-1 Discriminatory Assay (Gen-Probe Inc) Individual NAAT also performed 2/05 -present: independently validated real-time RT-PCR assay Individual NAAT when acute HIV suspected
Methods: Retrospective testing ● Serum stored for confirmatory testing and quality control ● First Ora. Quick-neg/EIA-pos tester identified in 11/05 by NAAT ● After 11/05, Ora. Quick-neg MSM tested by EIA before NAAT to reduce time/costs for pooled HIV NAAT to decrease time to receive HIV-positive results Other retesting 3 rd gen. EIA (HIVAB HIV-1/HIV-2 (r. DNA) EIA, Abbott Laboratories) Other rapid tests Clearview HIV 1/2 Stat. Pak (Inverness Medical Prof. Diagnostics) Uni-Gold Recombigen HIV-1 Test (Trinity Bio. Tech)
False negative EIA and Ora. Quick results: Data Needs for Strategy #3 -1 Standard testers (MSM) Cumulative # HIV-positive Cumulative N= 7437 “Sensitivity”* EIA 148 (2. 0%) 148 93% NAAT 10 (0. 1%) 158 99% Rapid testers (MSM) N= 5460 # HIV-positive Cumulative “Sensitivity” Ora. Quick 123 (2. 3%) 123 83% EIA 10 (0. 2%) 133 89% NAAT 16 (0. 3%) 149 100% *False-positive HIV NAAT = 0, False-negative HIV NAAT = 1 Individual NAAT: no additional cases in first 16 months of program
False positive test results (EIA): Data Needs for Strategy #3 -2 EIA-positive and WB “indeterminate” 1) Multiple “faint” bands, known HIV-pos = 2) “Faint” gp 120/160 – later confirmed = 3) “Faint” p 24, gp 55, gp 160 – confirmed = 4) p 40, RNA negative = 5) p 66, RNA negative = 6) gp 160, RNA negative (vaccine study) = 7) p 18, RNA negative, 3 month f/u negative = Standard testers N= 7437 EIA-positive EIA-negative HIV-positive 151 11 true positive false positive Sensitivity = 93. 2% HIV-negative Specificity = 99. 9% 4 PPV = 97. 4% 7271 NPV = 99. 8%
False positive test results (Ora. Quick): Data Needs for Strategy #3 -2 Unconfirmed Ora. Quick results 1) Refused blood draw (n=5) 2) Confirmatory test elsewhere = 3) Indeterminate WB (p 18, p 55, gp 160) = 4) Indeterminate rapid test = 5) Negative EIA/NAAT = Rapid testers N= 5455 HIV-positive Ora. Quick-positive 125 Ora. Quick-negative 26 true positive false positive (n=2) false positive Sensitivity = 82. 8% HIV-negative Specificity = 99. 9% PPV = 97. 7% 3 NPV = 99. 5% 5301
Results: retesting frozen sera from MSM with acute HIV infection # with acute HIV infection HIV-positive on retesting by 3 rd generation EIA 3 of 11 (27%) by Ora. Quick 0 of 6
Number and % with discordant Ab test results: Data Needs for Strategy #3 -3 Rapid testers N= 5455 EIA-pos EIA-neg Ora. Quick-pos 125 3 Ora. Quick-neg 11 5317 HIV-infected 0/3 (0%) EIA-/OQ+ 10/11 (90. 9%) EIA+/OQ(vaccine study participant)
Results: Ora. Quick-negative/EIA-positive testers EIA 1) Vironostika 2) Vironostika 3) r. LAV EIA 4) r. LAV EIA 5) r. LAV EIA 6) r. LAV EIA 7) r. LAV EIA 8) r. LAV EIA 9) r. LAV EIA 10) r. LAV EIA gp 120/160 S/CO 6. 2 2. 4 4. 7 5. 2 6. 4 4. 7 4. 3 6. 6 6. 0 WB p 24, p 51, gp 160 p 24, p 55, gp 160 p 18, p 24, p 55, gp 160 p 24, p 65, gp 160 p 24, faint gp 160 (indet) p 24, gp 160 p 24, p 55, gp 120/160 p 24, p 32, gp 41, p 55,
Results of rapid HIV antibody tests on frozen sera from MSM with early HIV infection Clearview Clinical Cases Ora. Quick-neg/EIA-pos Positive (n=5) EIA-pos/gp 41 -neg (n=5) EIA-pos/gp 41 -pos (n=5) Ora. Quick Uni-Gold Weak positive (2) (5) Positive (2) Positive (3) Strong positive (1) Weak positive (2) Positive (4) Positive (3) Strong positive (1) Positive (1) Strong positive (4) Strong positive (5) “weak positive”: barely visible “positive”: visible “strongly positive”: easily visible (specimen test line < positive control) (test line ≥ positive control but < external control) (test line reactivity ≥ external control)
Results (incidence/time) NAAT window period = 14 days EIA window period = 35 days Test “sensitivity” by test frequency HIV Test Quarterly Semi-annually Annually HIV Ab 72% 84% 91% HIV NAAT 86% 93% 96% Assumptions: 1) Timing of testing is uniform 2) Testing is independent of risk
Conclusions 1) No HIV test has a sensitivity of 100%. HIV NAAT will appear to be more effective with less sensitive Ab tests. 2) Ora. Quick may be less sensitive than 1 st or 2 nd generation EIAs in early HIV infection. Other rapid tests did not clearly perform any differently on stored sera. 3) As testing increases, sensitivity decreases because of a greater likelihood of testing during the “window period”. It is relatively more important to use the most sensitive tests in populations with frequent HIV testing and high rates of HIV acquisition.
Acknowledgements Clients and providers at the Gay City Health Project, PHSKC STD Clinic, and other PHSKC testing sites. Mentors Ann Collier Matt Golden Funding: The HIV NAAT pilot study was partially supported by Gen. Probe Incorporated from 9/03 -2/05. Grants: NIH K 23 AI-65243 UW CFAR: NIH AI-27757
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