Performance evaluation of the point-of-care INSTI™ HIV-1/2 antibody test in early and established HIV infections

•INSTI was accurate at detecting HIV-1 and HIV-2 antibodies.•INSTI detected more early HIV-1 infections than antibody-based lateral flow tests.•In whole blood, INSTI performs similarly to plasma.

BackgroundThe flow-through INSTI™ HIV-1/HIV-2 Rapid Antibody (INSTI) test is a 60 s FDA-approved test for HIV-1 and HIV-2 antibody testing using whole blood and plasma.ObjectiveWe evaluated the performance of INSTI using plasma and simulated whole blood specimens.Study designINSTI's performance in plasma specimens from commercial seroconversion panels was assessed by estimating the relative sensitivity using a 50% cumulative frequency analysis and by comparing its performance with other FDA-approved rapid tests (RTs). INSTI was further evaluated using 320 HIV-1 plasma specimens collected during a cross-sectional study and with 107 HIV-1 and 24 HIV-2 simulated whole blood specimens. Sensitivity and specificity were calculated using 615 known HIV-1 group M/O and 80 HIV-2 (Western blot (WB)-positive), and 497 HIV-negative plasma specimens, respectively.ResultsIn HIV-1 seroconversion panels, INSTI became reactive 9 days before a positive WB. When compared to FDA-approved antibody-based lateral flow RTs, INSTI detected significantly more early infections. Among HIV-1-infected cross-sectional plasma samples, INSTI detected 23 (27%) of 85 Architect-positive/Multispot-negative or indeterminate specimens. For plasma specimens, the sensitivity was 99.84% for HIV-1 and 100% for HIV-2, and the specificity was 99.80%. Using simulated whole blood from seroconverters, INSTI performed similarly to plasma.ConclusionsINSTI performed significantly better than antibody-based lateral flow RTs during early stages of seroconversion. Sensitivity and specificity were within the manufacturer's reported ranges. Considering the observed test performance and the almost immediate results, INSTI is an accurate option to detect HIV-1/HIV-2 antibodies in point-of-care settings where lab testing is not feasible.