The Resurgence of Syphilis: A 20-Year Evaluation of Epidemiological Trends and Serological Test Performance Using Rapid Plasma Reagin and Indirect Hemagglutination Assays.

: This retrospective single-center study aimed to evaluate the epidemiological, clinical, and laboratory characteristics of syphilis cases diagnosed at our hospital between 2005 and 2024, with a focus on the performance of serological tests used for diagnosis. The study also sought to characterize changing epidemiological trends of syphilis over this 20-year period. : Data from 671 patients with confirmed syphilis diagnoses were retrospectively analyzed. Demographic information, transmission routes, co-infection status, and serological test results-including Rapid Plasma Reagin (RPR) and Indirect Hemagglutination Assay (IHA)-were evaluated. Statistical analyses were performed using chi-square and Fisher-based tests, with Bonferroni correction applied for multiple comparisons : Of the 671 cases, 74.6% were male and 25.4% female, with the highest incidence in the 22-41 age group. The number of diagnosed cases increased approximately 6-fold after 2016 compared to the preceding years. Unprotected sexual contact was the most common transmission route. HIV co-infection was present in 32.6% of cases, predominantly in males. Significant differences in RPR and IHA titers were observed across clinical stages of syphilis, with notably higher titers in late latent and neurosyphilis cases. : The 6-fold increase in syphilis diagnoses since 2016, alongside a high rate of HIV co-infection, underscores the need for targeted prevention and screening programs for high-risk populations. Serological testing remains essential for diagnosis and disease monitoring.