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Diagnostic performance of two rapid tests for syphilis screening in people living with HIV in Cali, Colombia
Jonny Alejandro García Luna1,2,3, Nelson Romero-Rosas1, Sebastian Alejandro Silva Peña1
1Centro Internacional de Entrenamiento e Investigaciones Médicas - CIDEIM, Cali, Colombia.
Insights
Rapid diagnostic tests (RDTs) show excellent performance for syphilis screening in people living with HIV (PLWH). Determine RDTs perform better using serum than capillary blood, with considerations for implementation.
Area of Science:
- Infectious Diseases
- Public Health
- Diagnostic Medicine
Background:
- Syphilis co-infection is a significant concern for people living with HIV (PLWH).
- Evidence for the efficacy of rapid diagnostic tests (RDTs) for syphilis in PLWH is limited.
- Accurate and accessible diagnostic tools are crucial for managing syphilis in this population.
Purpose of the Study:
- To evaluate the diagnostic performance of two commercial syphilis RDTs (Bioline and Determine) in PLWH.
- To compare the performance of RDTs using capillary blood versus serum samples.
- To assess factors influencing RDT accuracy in a Colombian cohort.
Main Methods:
- A cross-sectional validation study was conducted on 244 PLWH in Cali, Colombia.
- Two RDTs (Bioline and Determine) were tested on both capillary blood (CB) and serum.
- A reference standard combining ELISA and TPHA was used, with RPR and clinical criteria for active syphilis.
Main Results:
- Both RDTs demonstrated high sensitivity and specificity for syphilis screening in PLWH.
- Determine RDTs showed significantly higher sensitivity with serum compared to capillary blood (99.1% vs 87.5%).
- Lower sensitivities were observed in patients not on antiretroviral therapy (ART) and with specific operators.
Conclusions:
- Commercially available RDTs exhibit excellent performance for syphilis screening and potentially active syphilis detection in PLWH.
- Serum samples are recommended over capillary blood for the Determine RDT to maximize sensitivity.
- Implementation of RDTs requires consideration of patient characteristics and operator-related factors for accurate interpretation.
Introduction:
There is insufficient evidence supporting the use of rapid diagnostic tests (RDTs) for syphilis in people living with HIV (PLWH). We evaluated the diagnostic performance of two commercially available RDTs (Bioline and Determine) in PLWH in Cali, Colombia.
Methods:
A cross-sectional field validation study on consecutive adults with confirmed HIV diagnosis attending three outpatient clinics. Both RDTs were performed on capillary blood (CB), obtained by finger prick, and sera, by venipuncture. A combination of treponemal enzyme linked immunosorbent assay (ELISA) and Treponema pallidum haemagglutination assay (TPHA) on serum samples was the reference standard. Rapid plasma reagin (RPR) and clinical criteria were added to define active syphilis. Sensitivity and specificity, predictive values and likelihood ratios (LR) of RDTs were estimated with their corresponding 95% confidence interval (95% CI). Stratified analyses by sample type, patient characteristics, non-treponemal titers, operator and re-training were performed.
Results:
244 PLWH were enrolled, of whom 112 (46%) had positive treponemal reference tests and 26/234 (11.1%) had active syphilis. The sensitivities of Bioline on CB and sera were similar (96.4% vs 94.6%, p = 0.6). In contrast, Determine had a lower sensitivity on CB than sera (87.5% vs 99.1%, p<0.001). Sensitivities were lower in PLWH not receiving ART (Bioline 87.1% and Determine 64.5%, p<0.001) and for one of the operators (Bioline 85% and Determine 60%, p<0.001). Specificities of the RDTs were > 95% in most analyses. Predictive values were 90% or higher. For active syphilis, the RDTs showed a similar performance pattern but with decreased specificities.
Conclusion:
The studied RDTs have an excellent performance in PLWH to screen for syphilis and potentially for active syphilis, yet Determine performs better on sera than CB. Patient characteristics and potential difficulties operators may face in acquiring enough blood volume from finger pricks should be considered for the implementation and the interpretation of RDTs.
