1. Performance of rapid HIV tests used singly and in combination: Moving toward a point of care diagnosis. Kevin Delaney, MPH HIV Diagnostics: New Developments and Challenges March 1, 2005

2. Background Rapid test combinations –Many countries throughout the world use multi-test algorithms for HIV confirmatory testing 4 FDA-approved tests –2 CLIA-waived –more likely on the way US experience to date –“Traditional” outreach testing → Rapid testing –Provide immediate results Negative “Preliminary Positive”

3. Background All FDA approved rapid HIV test package inserts now state: “This test is suitable for use in multi- test algorithms designed for statistical validation of rapid HIV test results. When multiple rapid HIV tests are available, this test should be used in appropriate multi-test algorithms.”

4. Objectives Describe the performance of individual rapid tests –Sensitivity, specificity and predictive value Evaluate the performance of combinations of rapid tests used in sequence –Particular focus on tests designed for use at point of care Foster discussion of a point of care diagnostic algorithm

5. Location –Two clinics in Los Angeles, CA Participants –Persons of unknown serostatus seeking HIV testing –Persons known to be HIV positive Methods

6. Testing –Multiple specimens from participants were tested with several rapid tests including: Multispot (Serum and plasma)* Oraquick (Oral fluid, whole blood and plasma) Reveal (Serum and plasma) STAT-PAK (Whole blood and plasma) Unigold (Whole blood and plasma)* Methods

7. Testing –Serum also tested with EIA and Western blot: Vironostika HIV-1 Microelisa system Genetic Systems HIV-1 Western Blot Samples of both serum and plasma retained for future testing (e.g. RNA NAT, DNA NAT, other EIAs) Methods

8. Analysis –Single rapid test results compared to EIA/WB Sensitivity, specificity and predictive value –Rapid test algorithms simulated using results of rapid tests as if they were performed sequentially Specificity and predictive value positive Methods

9. Initial Rapid Test Screen 2 nd Rapid test Screen Third Rapid Test “Tie- Breaker” Confirmed Positive Confirmed Negative Negative Positive Negative Positive Sequential Antibody Screening Algorithm

10. Sample Size ≈ 4800 total participants (including known positives) ≈ 4400 total participants Not on antiretroviral therapy ≈ 2400 total participants tested ≈ 800 EIA/WB+≈ 4000 EIA Negative ≈ 400 positives on treatment

11. Results – Sensitivity TestSpecimen type RT +False neg Sensitivity (95% CI) OraquickOral fluid400299.5 (98.2-99.9) Whole blood4010100 (99.3-100) UnigoldWhole blood139199.3 (96.1-100) Plasma245199.6 (97.8-100) Stat-pakWhole blood257398.9 (96.7-99.8) Plasma366299.5 (98.1-99.9) RevealSerum397299.5 (98.2-99.9)

12. Results – Sensitivity TestSpecimen type RT +False neg Sensitivity (95% CI) OraquickOral fluid400299.5 (98.2-99.9) Whole blood4010100 (99.3-100) UnigoldWhole blood 139 199.3 (96.1-100) Plasma245199.6 (97.8-100) Stat-pakWhole blood257398.9 (96.7-99.8) Plasma366299.5 (98.1-99.9) RevealSerum397299.5 (98.2-99.9)

13. Results – Specificity, single rapid test TestSpecimen type RT neg False + Specificity (95% CI) OraquickOral fluid41561100 (99.9-100) Whole blood41711100 (99.8-100) UnigoldWhole blood22820100 (99.9-100) Plasma22880100 (99.9-100) Stat-pakWhole blood34420100 (99.9-100) Plasma3435299.9 (99.8-100) RevealSerum4155399.9 (99.6-100) MultispotPlasma4870100 (99.4-100)

14. Results – Specificity, POC rapid tests TestSpecimen type RT neg False + Specificity (95% CI) OraquickOral fluid41561100 (99.9-100) Whole blood41711100 (99.8-100) UnigoldWhole blood22820100 (99.9-100) Stat-pakWhole blood34420100 (99.9-100)

15. Results – Specificity, POC rapid tests TestSpecimen type RT neg False + Specificity (95% CI) OraquickOral fluid41561100 (99.9-100) Whole blood41711100 (99.8-100) UnigoldWhole blood 2282 0100 (99.9-100) Stat-pakWhole blood34420100 (99.9-100)

16. PV+ Results – Predictive value positive, single rapid test Prevalence

17. Results – Sequential testing, 1 st test TestsAlgorithm ResultsComparison to EIA/WB 1 st test-+ OQ-b2234135 OQ-b2234136 OQ-o2235135 OQ-o2235135 UG2235135 UG2235135 UG2235135 SP2238133 SP2238131 SP2238132

18. Results – Two tests used sequentially TestsAlgorithm ResultsComparison to EIA/WB 1 st test 2 nd test - nd ++++ +-+- OQ-b UG 2234 1332 OQ-b SP 2234 1324 OQ-o UG 2235 1332 OQ-o SP 2235 1314 UG OQ-b 2235 1350 UG OQ-o 2235 1341 UG SP 2235 1323 SP OQ-b 2238 1321 SP OQ-o 2238 1310 SP UG 2238 1320

19. TestsAlgorithm ResultsComparison to EIA/WB 1 st test 2 nd test 3 rd test - nd + nd +-++-+ +--+-- OQ-bUG SP 2234133 11 OQ-bSP UG 2234132 31 OQ-oUG SP 2235133 11 OQ-oSP UG 2235131 31 UGOQ-b2235135 00 UGOQ-o SP 2235134 10 UGSP OQ-b 2235132 30 OQ-o 2235132 30 SPOQ-b2238132 00 SPOQ-o UG 2238131 10 SPUG2238132 00 Results – Adding the 3 rd test

20. TestsAlgorithm ResultsComparison to EIA / WB 1 st test 2 nd test 3 rd test - nd + nd +-++-+ +--+-- False Pos False Neg OQ-bUGSP223413311 00 OQ-bSPUG223413231 00 OQ-oUGSP223513311 01 OQ-oSPUG223513131 01 UGOQ-b223513500 00 UGOQ-oSP223513410 00 UGSPOQ-b223513230 00 OQ-o223513230 00 SPOQ-b223813200 00 SPOQ-oUG223813110 03 SPUG223813200 03

21. PV+ Results – Predictive value positive, single rapid test v. multitest algorithm Prevalence

22. Imperfect “Gold Standard” (EIA/Western blot) –Clinical follow-up is the “true gold” standard –Plan perform additional testing on residual specimens to address sensitivity of gold standard Lack of complete testing data for all specimens Testing was performed by trained technicians –Not counselors, nurses or others who might do testing in outreach settings Limitations

23. Sensitivity of all rapid tests was >98% –Comparable to current EIAs –Negative predictive value suggests < 2 false negatives/10,000 negatives tested @ 1% prevalence –Important to consider “realized sensitivity” Specificity of a single rapid test >99% –At low prevalence, the proportion of positive tests that are false positive increases. –Adding a second different rapid test increased specificity to 100% for specimens reactive on both tests –0-4 specimens required a third “tie-breaker” rapid test Summary

24. Data suggest ANY combination of rapid tests gives results comparable to EIA/Western blot algorithm –Use of combinations of waived tests would allow for POC testing and immediate return of confirmed results for both negatives and positives –Cost of rapid tests ≈ ½ cost of a Western blot; suggesting opportunity for significant cost savings –Other factors warrant consideration (e.g. CLIA status, ease of use, biohazards with different specimen types, shelf life, differentiation of HIV-2) Discussion

25. Need clinical follow-up of persons with discordant results – the true gold standard Evaluate on larger numbers Compare the sensitivity of rapid tests to NAT, 3 rd and 4 th generation EIAs Validate use of a POC diagnostic algorithm in a variety of field and clinical settings Next Steps

26. For discussion –M–More pros and any cons –I–Implementation barriers What do we need to do to catch up to Zimbabwe and Botswana? Outstanding Questions