Diagnostic performance of two rapid tests for syphilis screening in people living with HIV in Cali, Colombia

Abstract

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.

Advancing Syphilis Research: Exploring New Frontiers in Immunology and Pharmacological Interventions

“…Despite their widespread use, NTTs, including the RPR, may exhibit reduced sensitivity, particularly in cases with low titers [61]. Additionally, false-positive results can occur in specific conditions [62].…”

“…It is particularly important to consider these limitations when dealing with critical key populations, such as sex workers, who may be at increased risk of syphilis but could present with varying antibody levels. Sekure rapid plasma reagin (RPR-S) offers the advantage of rapid results, but its sensitivity and accuracy may require improvement before it can be considered a reliable tool for diagnosing syphilis and evaluating treatment efficacy in clinical practice [62]. Therefore, cautious consideration of its use is warranted.…”

Prevalence of HIV, Treponema pallidum and Their Coinfection in Men Who Have Sex with Men, Medellín-Colombia

“…8 , 9 The incidence of syphilis is approximately 300 per 100,000 people, with prevention, diagnosis, and treatment efforts primarily focused on pregnant women and their children, leading to a lack of solid data on syphilis in the general population or at-risk groups. 10 …”

“…8,9 The incidence of syphilis is approximately 300 per 100,000 people, with prevention, diagnosis, and treatment efforts primarily focused on pregnant women and their children, leading to a lack of solid data on syphilis in the general population or at-risk groups. 10 In terms of research, several studies have highlighted a high prevalence of co-infection with HIV and Treponema pallidum. In Asia, a systematic review in 2023 showed a prevalence of 3.0%.…”