1. Newborn Screening Quality Assurance Program Newborn Screening Quality Assurance Program Comparison of Less Sensitive HIV Incidence Tests for the Serological Testing Algorithm for Recent HIV Seroconversion (STARHS) J. Schiffer, B. Byers, B. Branson, S. Ethridge, K. Delaney, J. Mei Comparison of Less Sensitive HIV Incidence Tests for the Serological Testing Algorithm for Recent HIV Seroconversion (STARHS) J. Schiffer, B. Byers, B. Branson, S. Ethridge, K. Delaney, J. Mei Centers for Disease Control and Prevention Atlanta, GA 30341 Centers for Disease Control and Prevention Atlanta, GA 30341

2. Background STARHS uses a modified protocol of the bioMerieux Vironostika HIV-1 MicroElisa system (V-LS)- To be replaced in 2005 We investigated the comparability of the replacement test, Vironostika HIV-1 Plus O (VPlusO-LS) Longitudinal specimens from the HIVNET Infected Participant Cohort (IPC) were tested using both kits

3. Methods IPC specimen set 1009 specimens from 105 recent seroconverters Known dates of last negative and first positive HIV test Tested in triplicate on both assays

4. Methods Window Period Calculation –324 specimens from 59 patients 3 or more specimens collected before starting antiretroviral therapy (Mean length of follow up 504 Days) Mean window period definition –Number of days between detection of HIV antibody with a standard EIA and a threshold SOD of 1.0 with the LS-EIA

5. Results V-LS classified 459 samples as incident (SOD<1), and VplusO classified 472 as incident (90.2% concordance). Specimen SOD’s diminished after patients started antiretroviral therapy.

6. V-LS vs. VplusO-LS Sqrt SOD y = 0.996x + 0.0356 R 2 = 0.8482 0 0.5 1 1.5 2 2.5 3 3.5 00.511.522.53 V-LS Sqrt SOD VplusO-LS Sqrt SOD

7. Table 1: Window Period and Confidence Intervals for LS Tests Vironostika-LSVironostika Plus O-LS SOD Cutoff Window Period 95% Confidence Interval N (Patients, Samples) Window Period 95% Confidence Interval N (Patients, Samples) 0.7157140-18959, 314142127-15759, 324 0.8179157-20259, 314163149-18459, 324 0.9198174-22459, 314183167-21859, 324 1218193-25059, 314203185-24359, 324 1.1241214-27559, 314225203-26459, 324

8. Two-Year Rule SODs tended to plateau or decline after 2 years from last negative specimen. May result in longer window periods New window periods calculated excluding specimens collected after 2 years from last negative test

9. Window Period (SOD = 1) 95% Confidence Interval N (Patients, Samples) Vironostika-LS (IPC, 2 year cutoff) 212187-24459, 290 Vironostika Plus O-LS (IPC, 2 year cutoff) 196177-22859, 294 Vironostika-LS (SFMHS, 2003) 170145-20048, 227 Table 2 Window periods and confidence intervals for V-LS and VplusO-LS calculated with the two year cutoff rule applied to the IPC sample set. The V-LS window period previously published using the SFMHS sample set (Kothe et al. 2003) is shown for comparison.

10. Acknowledgements Chip Sheppard and Sean Watson of the California Department of Health Services for providing the HIVNET IPC specimens, without which this work would not have been possible. We would also like to thank Debra Kuehl, Silvina Masciotra, Hetal Patel, and Donna Rudolph for their help with organizing and aliquoting the IPC sample set