Sensitivity and specificity of two investigational Point of care tests for Syphilis and HIV (PoSH Study) for the diagnosis and treatment of infectious syphilis in Canada: a cross-sectional study

Abstract

ObjectivesSingle-visit testing and treatment for syphilis can reduce follow-up visits. The objectives of this study were to evaluate the performance and treatment outcomes of two dual syphilis/HIV point-of-care tests (POCTs). MethodsParticipants aged 16 years and older were offered concurrent syphilis/HIV POCTs with fingerstick blood sampling using two extremely rapid (<5 minutes) devices (MedMira Multiplo Rapid TP/HIV test and INSTI Multiplex HIV-1/HIV-2/Syphilis Antibody Test). Those with positive POCT results were offered same-day syphilis treatment and linkage to HIV care. Nurses performed testing at two emergency departments, a First Nations community, a correctional facility, and a sexually transmitted infection clinic. POCT results were compared with those of standard serological testing. Sensitivity and specificity were calculated. ResultsBetween August 2020 and February 2022, 1526 visits were completed. Both POCTs accurately identified participants with HIV (sensitivity, 100% [24 of 24]; 95% CI, 86.2–100%; specificity, 99.6% [1319 of 1324]; 95% CI, 99.1–99.8%), linking 24 HIV cases to care. Both tests were most sensitive with a rapid plasma reagin (RPR) of ≥1:8 dilutions (Multiplo: sensitivity, 98.3% [231 of 235]; 95% CI, 95.7–99.3%; specificity, 99.5% [871 of 875]; 95% CI, 98.8–99.8%; INSTI Multiplex: sensitivity, 97.9% [230 of 235]; 95% CI, 95.1–99.1%; specificity, 99.8% [873 of 875]; 95% CI, 99.2–99.9%) and least sensitive with non-reactive RPR (Multiplo: sensitivity, 54.1% [59 of 109]; 95% CI, 44.8–63.2%; specificity, 99.5% [871 of 875]; 95% CI, 98.8–99.8%; INSTI Multiplex: sensitivity, 28.4% [31 of 109]; 95% CI, 20.8–37.5%; specificity, 99.8% [873 of 875]; 95% CI, 99.2–99.9%). Eighty-five percent of participants with infectious syphilis were treated on the same day as the positive POCT result. DiscussionTwo extremely rapid (<5 minutes) dual syphilis/HIV POCTs showed excellent sensitivity and specificity for the diagnosis of active syphilis (RPR, ≥1:8 dilutions) and HIV and confirmed the ability to offer single-visit testing and treatment for syphilis and linkage to HIV care in diverse clinical settings.