Background Point-of-care tests provide immediate results with the opportunity for same-day interventions with improved public health outcomes. A dual HIV/syphilis test enables early treatment of both diseases.
Methods We conducted a field evaluation of the Standard Diagnostics' SD Bioline HIV/Syphilis Duo test (SD Bioline) among female sex workers. SD Bioline was conducted on finger-prick blood according to manufacturer's instructions and compared with (i) Genscreen HIV1/2 (third generation) and Vironostika Ag/Ab (fourth generation) assays for HIV, and (ii) Treponema pallidum particle agglutination (TPPA) and rapid plasma reagin (RPR) assays for syphilis. A negative TPPA test was considered negative, a TPPA-confirmed RPR titre ≤1:4 as past infection and a TPPA-confirmed RPR titre ≥1:8 as active syphilis. Sensitivity, specificity, positive and negative predictive values were calculated.
Results Of 263 women recruited, 14 (5.3%) declined an HIV test. Among the remaining 249 women, 187 (75.1%) were HIV positive, 51 (20.5%) had syphilis antibodies with seven (2.8%) active infections. For HIV, the sensitivity and specificity were 98.9% (95% CI 95.8% to 99.8%) and 100% (95% CI 92.7% to 100%). For syphilis, the sensitivity and specificity were 66.7% (95% CI 52.0% to 78.9%) and 98.0% (95% CI 94.5% to 99.3%). Sera with high TPPA titres were more likely to test positive.
Conclusions In field conditions, while the SD Bioline test has high sensitivity and specificity for HIV and high specificity for syphilis, the test has lower sensitivity for syphilis than reported from laboratory evaluations. As the dual test detects only two thirds of syphilis cases, it should only be used in areas with weak screening programmes.
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Handling editor Jackie A Cassell
Contributors VB, DAL, FR and VM conceptualised the study and wrote the protocol and conducted the work for the study; VB and BGW analysed the data; VB, BGW and DAL wrote the manuscript; VB, BGW, DAL and HVR edited the manuscript.
Funding The work was supported by the President's Emergency Plan for AIDS Relief, United States of America and AIDS Fonds, the Netherlands. SD Bioline tests were provided by Standard Diagnostics although the company had no input into the analysis or writing of this paper.
Competing interests None declared.
Ethics approval Human Research Ethics Committee University of Witwatersrand. Protocol number M130907.
Provenance and peer review Not commissioned; externally peer reviewed.
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