Prevalence and diagnostic accuracy of syphilis screening in blood donors: A prospective observational study comparing three different serological platforms

BACKGROUND AND OBJECTIVES: Transfusion-transmitted syphilis remains a concern, necessitating robust screening. This study evaluates the prevalence of syphilis among blood donors using electrochemiluminescence immunoassay (ECLIA), rapid diagnostic card test (RDT) and venereal disease research laboratory (VDRL) tests, comparing their diagnostic performance. MATERIALS AND METHODS: A prospective observational study was conducted on 10,403 donors by ECLIA. Reactive samples underwent RDT and VDRL testing. Additionally, 100 ECLIA-negative controls were retested to assess test specificity as well as internal validation. Qualitative and quantitative VDRL testing were performed. Correlations between ECLIA cut-off index (COI) values and VDRL titres were analysed. Statistical analyses included descriptive statistics, Chi-square tests as well as receiver operating characteristic (ROC) curve and area under the curve (AUC) for each method. RESULTS: Syphilis prevalence was 1.05% (109/10,403) by ECLIA. Of these, 85% were RDT-reactive and 60.5% VDRL-reactive. All ECLIA-negative controls were non-reactive in RDT and VDRL. VDRL showed 83.3% sensitivity, 97.7% specificity and an AUC of 0.950. RDT demonstrated 97.8% sensitivity, 93.7% specificity and an AUC of 0.985. ECLIA COI values correlated strongly with VDRL titres (ρ = 0.822, p < 0.001). No significant association was found with gender or donor category. CONCLUSION: ECLIA proved to be a reliable primary screening tool for syphilis because of its high sensitivity and strong correlation with VDRL titres. RDT showed superior diagnostic accuracy compared to VDRL, supporting its use as a supplementary method in resource-limited settings. These findings highlight the need for robust screening strategies to enhance transfusion safety.