Performance of New Point-of-Care Syphilis Tests

Background: New rapid point-of-care (POC) tests are being developed that would offer the opportunity to increase screening and treatment of several infections, including syphilis.  This study, which was in response to a CDC opportunity in the Federal Register, evaluated three of these new rapid POC tests at a site in Southern California.

Methods: Participants were recruited from a testing center in Long Beach, California.  A whole blood specimen was used to evaluate the performance of the Dual Path Platform (DPP) Syphilis Screen & Confirm, DPP HIV-Syphilis, and DPP HIV-HCV-Syphilis rapid tests.  The gold-standard comparisons were Treponema pallidum passive particle agglutination (TPPA), rapid plasma reagin (RPR), HCV enzyme immunoassay (EIA), and HIV-1/2 EIA.

Results: A total of 870 whole blood specimens were analyzed in this study. The sensitivity of the HIV tests ranged from 95.0-100% and the specificity was 99.6-100%. The sensitivity and specificity of the HCV test were 91.3% and 99.4%, respectively.  The treponemal-test sensitivity when compared to TPPA ranged from 44.0-51.2% and specificity was 99.2-99.6%. The non-treponemal test sensitivity and specificity when compared to RPR was 42.9% and 98.8%, respectively.  The sensitivity of the Screen & Confirm test improved to 87.5% when cases who were both treponemal and nontreponemal positive on the POC test were compared to TPPA+/RPR >1:8 on the gold-standard.

Conclusions: The HIV and HCV on the multi-infection tests showed good performance, but the treponemal and nontreponemal tests had low sensitivity.  These results could be due to a low prevalence of active syphilis in the sample population.  The syphilis POC test did perform better when compared to detection of cases more likely to be active.  Further evaluation of the new POC tests is required before implementation into testing programs.