Background: Rapid, point-of-care tests that accurately identify syphilis are gaining popularity and offer several advantages over classic tests.
Methods: The SD Bioline Syphilis 3.0 and the Chembio DPP Syphilis Screen and Confirm Assay (CB) were assessed using 1283 samples that had been characterized by reference tests. The challenge samples included 5 commercial panels (seroconversion, mixed-titer), archived samples, fresh samples, and a dilution series. Both tests detect specific anti-treponemal antibodies, and the CB additionally detects antibodies to a non-treponemal (NT) component. The evaluation was used to determine performance indices and compare with those cited by the manufacturers.
Results: When assessing reactivity to treponemal, the sensitivities for the 2 tests were 98.3% and 93.2%, with specificities of 100% and 99.4%, respectively. For both tests, precision, whole blood testing, and high-temperature testing produced perfect results, and there were no invalid results. Comparisons of 2 different lots of each test indicated excellent concordance (100% and 99.5%), and reproducibility was 100% and 98.0%, respectively. For the CB, the sensitivity for the NT component was between 65.3% and 80.9%, but increased to 98.5% with samples having a rapid plasma regain (RPR) titer of ≥8. The specificity for NT was found to be 100%, and the reading of results visually and when using a battery-operated reader indicated a concordance for all challenges of 95%–100%.
Conclusions: Both rapid tests produced impressive results for the detection of antibodies to treponemal for all challenges and exceeded, met, or closely approached the performance characteristics as cited by the manufacturers.
Authors' Disclosures or Potential Conflicts of Interest: Upon manuscript submission, all authors completed the author disclosure form. Employment or Leadership: N.T. Constantine, University of Maryland. Consultant or Advisory Role: None declared. Stock Ownership: A. Sill, Chembio Diagnostic Systems. Honoraria: None declared. Research Funding: N.T. Constantine, United States Agency for International Development (USAID) and Family Health International 360 (FHI360); Chembio Diagnostic Systems provided test kits for this study. Expert Testimony: None declared. Patents: None declared.
Role of Sponsor: The funding organizations played no role in the design of study, choice of enrolled patients, review and interpretation of data, or preparation or approval of manuscript.
- Received July 22, 2016.
- Accepted October 13, 2016.
- © 2016 American Association for Clinical Chemistry