Evaluation of Treponema pallidum Hemagglutination Assay among Varying Titers of the Venereal Disease Research Laboratory Test

Background and Objective: Syphilis, besides being a significant cause of perinatal morbidity and mortality, is a substantial cause of adult morbidity. A discordant serological result can present a diagnostic challenge; hence, a fundamental knowledge about the diagnostic limitations or interpretation of these assays becomes imperative for the clinicians to avoid management dilemma. The study was proposed to see the usefulness and correlation of Treponema pallidum hemagglutination assay (TPHA) with varying titers of Venereal Disease Research Laboratory (VDRL) test. Materials and Methods: Over a period of 2 years, 22,351 sera were subjected to screening for syphilis by VDRL test. TPHA test was performed for confirmation in 243 of the total sera. Results: VDRL reactivity was seen in 0.77% of the tested sera. TPHA positivity was 58.85% among the sera tested. Calculated sensitivity, specificity, positive predictive value, and negative predictive value of VDRL against TPHA were 87.41%, 52%, 72.25%, and 74.29%, respectively. TPHA positivity was found to be 100% and 55% in VDRL reactive cases with titers >= 32 and <8, respectively. Conclusion: Screening and diagnostic serological tests for syphilis should be reviewed in routine by the treating physician in the light of clinical presentation and the history of infection and treatment.