Evaluation of the performance of the Abbott ARCHITECT HIV Ag/Ab Combo Assay

BackgroundWorldwide, many countries test for HIV infection using combination assays that simultaneously detect p24 antigen and HIV antibodies. One such assay, the ARCHITECT® HIV Ag/Ab Combo Assay (ARCHITECT), has recently been approved by the Food and Drug Administration (FDA) for use in the United States.ObjectiveTo evaluate the performance of ARCHITECT on well-characterized specimens from four CDC-funded studies.Study designWe evaluated 3386 HIV-infected, 7551 HIV-uninfected, and 58 acute HIV infection (AHI) specimens. HIV-infected specimens were repeatedly reactive by enzyme immunoassay (EIA) and Western blot (WB) or positive by nucleic acid amplification testing (NAAT). HIV-uninfected specimens were EIA- and NAAT-negative. AHI specimens were seronegative or indeterminate (using antibody-based EIAs, rapid tests or WB) and NAAT-positive. All specimens were de-identified and sent to Abbott Diagnostics for testing with ARCHITECT. ARCHITECT test results were compared to original study characterizations and were used to assess overall sensitivity and specificity and also sensitivity for AHI. ARCHITECT false-positive specimens with sufficient quantity were retested.ResultsBased on results from the initial ARCHITECT test, sensitivity was 99.94% (95% confidence interval [CI]: 99.79, 99.99) and specificity was 98.78% (95% CI: 98.51–99.01). Repeat testing resulted in corrected specificity of 99.50% (95% CI: 99.31, 99.64). Also, 48 AHI specimens (83%) were detected by this screening assay.ConclusionThe sensitivity and specificity of the ARCHITECT combination assay are very high and most AHIs were detected by the assay. Use of Ag/Ab combination assays may improve the number of AHIs identified relative to existing FDA-approved HIV-antibody only based serologic assays, particularly in high incidence populations.