Missed opportunities: HIV testing deficits among syphilis-tested patients in Japan

Japan faces dual challenges of rising syphilis incidence and persistent late HIV diagnoses, with approximately 30 % of new HIV cases identified at AIDS stage. This study analyzed HIV testing practices among syphilis-tested patients using National Database of Health Insurance Claims sampling data (2011–2020). Among 253,865 patients tested for syphilis, only 13,485 (5.31 %) underwent HIV testing. HIV testing rates showed a concerning age-related decline from 8.27 % in patients under 20 years to 4.67 % in those over 70 years (Cochran-Armitage trend test, p < 0.0001). This age-based disparity persisted across both sexes and showed no improvement over the study period (p = 0.24). Among 22,961 patients who received antibiotic treatment for any sexually transmitted infection (STI), only 905 (3.94 %) underwent HIV testing. The inverse relationship between testing rates and age is particularly alarming given that older patients have the highest risk of late HIV diagnosis, with 56.9 % of those over 70 diagnosed at AIDS stage compared to 10.0 % of those under 20. These findings reveal critical implementation gaps in HIV testing despite international guidelines recommending routine testing for all STI patients. The persistent low testing rates across all age groups, combined with systematic age-based disparities, indicate entrenched system failures requiring urgent policy intervention. Implementing opt-out HIV testing for all STI evaluations could substantially reduce missed opportunities for early HIV detection and improve public health outcomes.