Analysis of sexually transmitted infections in Japan using a hospital claims database

Background This study aimed to address two questions: (1) What is the distribution of diagnosing departments for sexually transmitted infections (STIs), and how might this affect care? (2) Are current government surveillance methods accurately capturing trends in STI infection rates? Methods This observational, retrospective study used claims data from Diagnosis Procedure Combination (DPC) hospitals. Patients diagnosed with syphilis, chlamydia, condyloma, or gonorrhea between April 2008 and January 2022 were included. Diagnosing departments were inferred from treatment orders, and variation was measured using the Shannon Index. Age, sex, and case distributions were compared to Ministry of Health, Labour, and Welfare (MHLW) surveillance reports. Results A total of 34,295 STI cases were identified in the hospital claims database, compared to 621,212 patients reported by MHLW. Syphilis showed the greatest variation in diagnosing departments (Shannon index = 1.89 for both males and females). Gender distribution differed most notably between datasets for chlamydia and condyloma, with a higher proportion of female cases in claims data. MHLW data lacked information on diagnosing departments. Conclusions STIs, especially syphilis, are diagnosed across diverse departments, highlighting the need for coordinated care. Differences between datasets suggest Japan’s sentinel surveillance may underrepresent some STIs.