Evaluation of RPR, TPHA and ELISA test results used in the diagnosis of syphilis at a university hospital

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Aims: This study aimed to evaluate the laboratory results of treponemal and non-treponemal serological tests used in the diagnosis of syphilis and to investigate the diagnostic contributions of different testing algorithms. Methods: Between April 2023 and June 2025, serum samples from 600 patients who underwent all three tests in the Microbiology Laboratory were retrospectively analyzed. The Rapid Plasma Reagin (RPR), Treponema pallidum Hemagglutination Assay (TPHA) and Enzyme-Linked Immunosorbent Assay (ELISA) tests were performed according to the manufacturers’ instructions, and the results were evaluated within both conventional and reverse algorithm frameworks. Results: In 89.5% of cases (n=537), all three tests were negative, while at least one test was positive in 10.5% (n=63). ELISA showed the highest positivity rate, with 63 reactive samples. A total of 20 cases were positive across all three tests simultaneously. Samples positive only by ELISA were notably increased in the age group over 60 years. RPR positivity was lower compared to treponemal tests. Within the reverse algorithm, discrepancies between ELISA-positive and RPR-negative results were observed at a notable frequency. Conclusion: Using treponemal tests as the first step in syphilis screening provides a more sensitive approach. Positive results should be confirmed with a second treponemal test, while non-treponemal tests are essential for assessing active infection and treatment monitoring. Higher ELISA positivity in older individuals suggests more false positives. The study underscores the need for laboratory–clinical collaboration and larger prospective studies.