Methods - Testing Antibody (Ab)-plus-RNA testing reference standard: The complete algorithm, including Ab and RNA test

1. 100% 98% 98% 96% 96% 94% 93% 94% 93% 92% 92% 91% 92% 90% Se 88% 86% 86% 84% 82% 80% 78% 1st Gen EIA Multi-Spot HIV 1/2 Clearview Stat-Pak Unigold Recombigen Oraquick Advance (Blood) Oraquick Advance (Oral Fluid) Genetic Systems HIV 1/2 Plus 0 ARCHITECT HIV Ag/Ab Combo Determine HIV-1/2 Ag/Ab Combo 992 A Clinical Study of Antigen-Antibody Rapid Testing for Acute HIV InfectionChristopher D. Pilcher1, Brian Louie2, Sheila Keating3, Mark Pandori2, Falk Fish4, Tomer Keren4, Sally Liska2, Michael P. Busch3, Frederick M. Hecht1, Jeffrey Klausner1,2 and Grant Colfax1,2from 1UCSF HIV/AIDS Division; 2SF Department of Public Health; 3Blood Systems Research Institute; 4Inverness Medical Innovations Acute HIV infections, as a proportion of all HIV cases detected Results by each testing program. The % of all HIV infected cases Background A key factor influencing HIV test performance, particularly in higher-risk testing sites, is the ability to detect acute HIV cases.  These cases are often negative on tests designed to detect only anti-HIV IgG “4th generation” immunoassays (e.g., the ARCHITECT HIV Ag/Ab Combo) can detect both HIV p24 antigen and anti-HIV antibodies for earlier detection. A new rapid test (the Determine HIV-1/2 Ag/Ab Combo) is also designed to detect HIV p24 antigen and anti-HIV antibodies. We sought to measure the potential impact of these new screening tests on the performance of real-world, public health and research testing programs in San Francisco. Methods - Testing Antibody (Ab)-plus-RNA testing reference standard: The complete algorithm, including Ab and RNA tests, was used to define HIV infection. The combined reference standard was used to determine Sensitivity, Specificity and Positive/Negative Predictive Values for each screening assay. Western blot was used to categorize samples as representing acute (WB negative/indeterminate) or established (WB positive) HIV infection. identified that were Western blot - negative or indeterminate is shown. The majority of RNA + patients found in high risk testing populations (high risk MSM, non-targeted STD clinic VCT, partner services and nPEP) were detectable by the 4th generation EIA or by the new rapid Ag/Ab combo assay, but not by 1st generation or even 3rd generation EIAs. 50% 45% 40% 40% 100% 1st Gen EIA 35% 90% Programs with the highest yield of acute HIV infections were those targeting patients with high risk exposures 80% Stat - Pak Rapid Screening HIV 30% + - 70% % Ab Test Genetic Systems HIV - 1/2 60% 25% % Acute Infections Positive on Each Test Plus 0 50% 20% Determine HIV - 1/2 Ag/ Ab 40% Combo Rapid 30% 15% ARCHITECT HIV Ag/ Ab 10% Ab Status Pooled RNA 20% - Combo + 10% 7% 10% 6% Confirmation 0% 5% HIV RNA nPEP 0% WB Realtime PCR STD Clinic nPEP High Risk MSM Partner Services High Risk MSM STD Clinic Partner Services Acute HIV Diagnostic Testing Population - San Francisco - + Sensitivity was compared head-to-head in the high risk MSM testing population, The sensitivity estimates associated with each rapid test (light blue) and central lab immunoassay (dark blue) are shown. Despite differences in clinical sensitivity, negative predictive values for each test to were >99.5%. Specificity was estimated to be 100.00% for all immunoassays. Oraquick Advance specificity was lower on oral fluid (Sp 99.86) vs. blood (99.96). The Determine HIV Ag/Ab Combo correctly identified 80 of 81 HIV negative Options specimens, with 1 false positive result (Sp 98.9). • Summary • In practice in San Francisco testing programs, HIV screening tests differed significantly in their ability to detect HIV infections. Assays that detected acute HIV substantially increased case identification. • The Determine® HIV-1/2 Ag/Ab Combo, a novel point of care assay, increased detection of HIV infection compared to all existing antibody-only rapid tests. Separate signals for HIV-1 p24 antigen and HIV antibodies make immediate, point of care identification of acute cases possible. Speed and simplicity make the test appropriate for both developed and developing world settings. • The ARCHITECT ® HIV Ag/Ab Combo, a 4th generation immunoassay, showed even greater sensitivity for acute HIV infections. This assay could eliminate the need for pooled HIV RNA for central laboratory screening of acute HIV infections. • Confirmatory algorithms must be modified (e.g., to incorporate HIV RNA), as these screening tests are more sensitive than established Western blot or immuno-fluorescence assays, and have imperfect specificity. • The Oraquick oral fluid test device (with an estimated sensitivity of 86%) may not be appropriate for testing of high risk individuals in San Francisco. HIV Ab (+) HIV Ab ( - ) RNA (+) HIV Ab ( - ) RNA ( - ) Established HIV Acute HIV HIV Negative Rapid Test Panel Methods - Specimens Testing programs were included that used both HIV antibody and HIV RNA amplification tests in their diagnostic algorithm: High Risk MSM, Targeted Testing Population (n=6661)— MSM at public testing sites meeting high risk criteria (sex with HIV+, unprotected anal intercourse, or STD) STD Clinic Population (n=14573)— attendees to the muncipal STD clinic, not meeting above criteria Non-occupational Post Exposure Prophylaxis (nPEP) Population (n=989)— patients evaluated for, or receiving, nPEP Partner Services (PS) Testing Population (n=173)— sexual or needlesharing partners to newly diagnosed HIV+ Acute HIV Diagnostic Testing Population (n=1114; 1998-2008)— patients screened for having acute HIV by the UCSF Options study based on acute retroviral symptoms and/or high risk exposure. Central Lab Test Panel Oraquick Advance 3 Gen EIA ( Gen Systems HIV ½ Plus O) rd Clearview Stat - Pak 4 Gen IA (Abbott ARCHITECT HIV Ag/ Ab Combo) th Unigold Recombigen Western Blot ( Biorad Genetic Systems) Multispot HIV 1/2 Determine HIV 1/2 Ag/ Ab Combo Head to head comparative performance evaluation: Acute specimens (RNA+, WB- or indeterminate) were submitted to Rapid Test and Central Lab panel tests. Sensitivity and Negative Predictive Values (NPV) were calculated for each panel test, assuming 100% detection of WB positive specimens. Determine HIV-1/2 Ag/Ab Combo: Rapid Test Readout Acknowledgements The work was supported by R01- MH068686; we are grateful to Shelley Facente for analysis and to John Hackett, Jr. for providing 4th generation IA data, previously submitted for publication (Pandori MW, Hackett Jr., Louie B, et al., as “Assessment of the Ability of a Fourth Generation Immunoassay for HIV Antibody and p24 Antigen to Detect both Acute and Recent HIV Infection in a High-Risk Setting.”)