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Field evaluation of the performance and testing costs of a rapid point-of-care test for syphilis in a red-light district of Manaus, Brazil
  1. Adele S Benzaken (abenzaken{at}fuam.am.gov.br)
  1. Fundação Alfredo da Matta, Brazil
    1. Meritxell Sabidó (xellsabido{at}gmail.com)
    1. London School of Hygiene & Tropical Medicine, United Kingdom
      1. Enrique G Galban
      1. Fundação Alfredo da Matta, Brazil
        1. Valderiza Pedroza
        1. Fundação Alfredo da Matta, Brazil
          1. Felicien Vasquez
          1. Fundação Alfredo da Matta, Brazil
            1. Adauto Araújo
            1. Escola Nacional de Saúde Pública/ENSP/FIOCRUZ, Brazil
              1. Rosanna W Peeling (peelingr{at}who.ch)
              1. World Health Organization, Switzerland
                1. Philippe Mayaud (philippe.mayaud{at}lshtm.ac.uk)
                1. London School of Hygiene and Tropical Medicine, United Kingdom

                  Abstract

                  Objectives: To assess the performance, usefulness and cost of a rapid treponemal antibody assay (VisiTect Syphilis) to detect syphilis in high-risk populations.

                  Methods: STI clinic attenders 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. Fingerprick 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 45.8-66.7), 99% (95%CI: 97.0-99.6), 91% (95%CI 80.0-96.7) and 91% (95%CI 88.0-93.5), 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 fingerprick 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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