M. Kathleen Shriver, PhD
R&D Manager, Redmond Operations, Bio-Rad LaboratoriesIssues: Manufacturers of licensed HIV test kits were challenged by FDA in 1996 to develop improved antibody screening assays containing specific antigenic sequences for detection of HIV-1 group O. This presentation describes the design and performance parameters of the Bio-Rad Genetic Systems™ HIV-1/HIV-2 PLUS O EIA, which was licensed in August, 2003 as a screening test for serum, plasma, and cadaveric serum specimens and as an aid in the diagnosis of infection with HIV-1 (Groups M and O) and/or HIV-2.Description: The HIV-1/HIV-2 PLUS O EIA combines specific recombinant and synthetic peptide antigens, representing HIV-1, HIV-2, and HIV-1 variant sequences, in a direct antibody capture format. The performance parameters of the new microplate assay, including sensitivity, specificity, and reproducibility, were evaluated in studies at six sites compared to current FDA-licensed tests for detection of HIV-1/HIV-2 antibody. HIV-1 sensitivity was estimated to be 100% based on the results of testing 313 patients with AIDS, as well as 490 HIV-1 positive samples from the U.S., and 199 HIV-1 positive samples from diverse regions outside the U.S. (total N=1002). All 77/77 (100%) HIV-1 Group O specimens and 302/302 (100%) known HIV-2 samples were correctly detected. In testing of HIV-1 seroconversion panels, 34/46 (74%) demonstrated at least one bleed improvement in detection by the new assay compared to a previously licensed test, and 12/46 (26%) were equivalent. All positive samples (N=130) from four commercial panels, representing low titer samples and/or HIV subtypes of worldwide origin, were detected by the new assay (100%), vs. 95.4% and 98.5% detection using other licensed HIV-1/HIV-2 tests. In testing of 11,159 normal donor samples, specificity was 99.89% (IR=0.16%, RR=0.11%).Lessons Learned: The new HIV-1/HIV-2 PLUS O EIA provides a significant improvement in sensitivity over previously licensed assays for detection of HIV antibody, while offering equivalent or better specificity. The improvement in sensitivity was demonstrated for samples containing HIV-1 Group O antibody, as well as challenging HIV-1 Group M seroconversions and low titer specimens.
The New Landscape of HIV Testing in Laboratories, Public Health Programs and Clinical Practice