Objectives: To assess the performance, usefulness and cost of a rapid treponemal antibody assay (VisiTect Syphilis) to detect syphilis in high risk populations.
Methods: People who attended STI clinics in Manaus, Brazil, were screened for syphilis using the fluorescent treponemal antibody absorption (FTA-Abs) test and a non-treponemal test (Venereal Diseases Research Laboratory (VDRL)), and for HIV. Finger prick blood samples were tested with VisiTect Syphilis. The rapid test was evaluated against the reference FTA-Abs and for its usefulness in detecting active syphilis (FTA-Abs and VDRL positive). Operational performance was assessed through providers’ and patients’ interviews. An economic evaluation was conducted from the provider’s perspective.
Results: 510 patients (60% men) were enrolled, of whom 13 (2.5%) were HIV-1 seropositive. Syphilis prevalence (FTA-Abs) was 18% and active syphilis prevalence was 7.5%. 11% (57/506) of samples were positive by VisiTect. The sensitivity, specificity, positive and negative predictive values of VisiTect Syphilis were 57% (95% CI 45.8 to 66.7), 99% (95% CI 97.0 to 99.6), 91% (95% CI 80.0 to 96.7) and 91% (95% CI 88.0 to 93.5), respectively. VisiTect Syphilis identified 79% (30/38) of active syphilis cases. The cost per case of syphilis was $16.8 for VDRL, $33.2 for low cost and $56.3 for high cost VisiTect Syphilis; the cost per case of active syphilis was $21.3, $57.5 and $97.6, respectively. Patients identified finger prick pain and preference for venous blood collection as minor barriers to test use.
Conclusion: VisiTect Syphilis had low sensitivity in field use and was less cost effective than conventional VDRL. However, rapid and correct identification of a high proportion of active syphilis cases combined with operational characteristics suggest a role in high risk populations.
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Funding: The study was supported by a grant from the UNICEF/UNDP/World Bank World Health Organization (WHO) Special Programme for Research and Training in Tropical Diseases.
Competing interests: None.
Ethics approval: The study was approved by the Ethics Review Committee of the World Health Organization (WHO), the Research Ethics Committees of FUAM and the London School of Hygiene & Tropical Medicine.
Contributors: ABS designed and supervised the overall study; MS designed and supervised the operational component of the study, conducted analyses and wrote the initial draft of the manuscript; EGG, AA, VP, FV conducted data analysis; RWP and PM were involved in study design, data interpretation and manuscript preparation. All authors revised and approved of the final contents of the manuscript.