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.
OBJECTIVE
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.


CONCLUSIONS
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.
Benzaken
A S
AS
Fundação Alfredo da Matta, Manaus, Brazil.
Sabidó
M
M
Galban
E G
EG
Pedroza
V
V
Vasquez
F
F
Araújo
A
A
Peeling
R W
RW
Mayaud
P
P
D001938:Brazil; D003365:Costs and Cost Analysis; D004797:Enzyme-Linked Immunosorbent Assay / Q000191:economics / Q000379:methods / Q000592:standards; D005260:Female; D006801:Humans; D008297:Male; D019095:Point-of-Care Systems / Q000191:economics / Q000592:standards*; D012680:Sensitivity and Specificity; D011477:Sex Work; D013587:Syphilis / Q000175:diagnosis* / Q000191:economics; D013588:Syphilis Serodiagnosis / Q000191:economics / Q000592:standards*