Syphilis prevalence among a large regional online postal self-sampling STI testing service (OPSS)

Objectives In England, infectious syphilis diagnoses have reached the highest annual number since 1948. Fifty per cent of syphilis testing is now provided through online postal self-sampling sexually transmitted infection (STI) testing services (OPSS). To reduce the burden of syphilis, we need to understand the syphilis prevalence and transition to treatment rates among service users of OPSS. This report aims to estimate syphilis prevalence among people accessing Sexual Health London (SHL), a regional, National Health Service (NHS)-funded OPSS. Methods Demographic, STI concurrency, sexual behaviour data and case outcomes were collected from SHL service users who received testing for syphilis between 8 March 2022 and 30 June 2023. Data were analysed to identify syphilis prevalence and transition to care rates. Results 458 520 syphilis tests were performed for 267 780 service users. 12 870 (2.8%) results were reactive. Their assigned case outcomes comprised: 10 048 (78.1%) past adequately treated syphilis; 971 (7.5%) treated for active syphilis; 1293 (10.1%) SHL results did not subsequently confirm and 558 (4.3%) had an unknown final outcome. Of unique users, 0.4% (940/267 780) received syphilis treatment at least once. They were: 89.3% aged >= 25 years, 87.3% male, 83.7% gay/bisexual. Co-infections identified were: chlamydia (14%), gonorrhoea (13.3%) and previously undiagnosed HIV (1.5%). 36.1% (339) took pre-exposure HIV prophylaxis, 30.1% engaged in sex parties/group sex and 26.8% had sex under the influence of drugs/alcohol. Individuals aged >= 35 years, of non-female gender, gay/bisexual, from indices of multiple deprivation (1-5) and from certain racially minoritised communities were statistically more likely to require treatment for syphilis than the overall testing population (p<0.05). Conclusion Estimated syphilis prevalence (0.4%) was comparable to rates within national sexual health clinics and the demographic characteristics of those most affected by syphilis were also similar. Further work is required to improve the integration between NHS OPSS and sexual health clinics and to enable OPSS to more accurately input data on treatment and diagnoses towards national surveillance statistics.