Long-term Trend of Serological Test for Syphilis in Our Health Examination Center

Abstract

Objective: Since 2013, the number of syphilis has been increasing in Japan. In Sapporo and Hokkaido, the number of syphilis cases increased rapidly in 2022. Therefore, we investigated the long-term trend of serological tests for syphilis in our health examination center.

Methods: The participants were individuals who underwent serological tests for syphilis between October 2016 and April 2024. Three types of TPLA reagents and one type of RPR reagent were used. TPLA(-) is defined as < 5 U/mL, 10 T.U. or 1.0 COI, whereas RPR(-) is defined as < 1.0 R.U.. TPLA(+) is defined as ≥ 5 U/mL, 10 T.U. or 1.0 COI, whereas RPR(+) is defined as ≥1.0 R.U.. Four patterns of the results were defined; TPLA(+)RPR(+) is currently infected, TPLA(+)RPR(-) is already infected, TPLA(-)RPR(+) is biological false-positive, and TPLA(-) RPR(-) is non-infected.

Results: The number of syphilis did not increase in our health examination center.

Conclusions: Although the number of syphilis cases is increasing in Japan, our center has not reported such increase. As health examinations be more important in the diagnosis of syphilis eventually, health examination workers should gain the correct knowledge.