Sexually transmitted infection testing and key outcomes following implementation of online postal self-sampling into sexual health services in England: a retrospective observational study of routinely collected service-level healthcare data.

Background: A shift to online postal self-sampling (OPSS) for sexually transmitted infections (STIs) in high-income settings has occurred. We evaluate whether introduction of OPSS in England is associated with changes in testing activity and if this differs by population characteristics. Methods: A retrospective study of sexual health (online and clinic-based) service-level data, across three case study areas (CSAs) that implemented OPSS at different times, using different models, and whose populations have different socio-demographic profiles, between 01/01/2015 and 31/12/2022 (from 01/08/2014 in CSA1 to ensure 12 months pre-OPSS). The primary outcome was chlamydia/gonorrhoea and HIV testing activity. We evaluated change over time using selected calendar years, with total activity following introduction of OPSS (2019 and 2022) compared to pre-OPSS periods (CSA1, 2014-2015, CSA2 2017, CSA3 2019), and whether outcome changes differed by socio-demographic characteristics. Findings: In all CSAs chlamydia/gonorrhoea and HIV testing activity increased following introduction of OPSS with incidence rate ratios (IRR) for chlamydia/gonorrhoea testing in 2022 compared to pre-OPSS baseline ranging from 2.1 (95% CI 2.1-2.2) in CSA1 to 2.5 (95% CI 2.4-2.5) in CSA3, and for HIV testing from 1.5 (95% CI 1.5-1.5) in CSA1 to 2.8 (95% CI 2.8-2.8) in CSA2. Differences existed across all demographic characteristics in the relative change in testing incidence (all P < 0.0001 for chlamydia/gonorrhoea). Higher testing activity via OPSS was seen among men who have sex with men (MSM), particularly in CSAs1-2 for chlamydia/gonorrhoea (IRR2.9 (95% CI 2.8-3.1) and 3.6 (95% CI 3.5-3.7) in MSM compared to 1.7 (95% CI 1.7-1.8)and 1.8 (95% CI 1.8-1.8) in men who have sex exclusively with women (MSEW) for 2022 vs pre-OPSS). In CSA3, the largest relative increase occurred in women (IRR 3.2 (95% CI 3.1-3.3), compared to IRR 1.9 (95% CI 1.8-1.9) in MSEW). The most deprived areas had the lowest relative increase in chlamydia/gonorrhoea testing uptake (1.9-2.1 for CSA1-3). Interpretation: Despite a reduction in clinic-based testing linked to COVID-19, the introduction of OPSS has been associated with increases in overall testing activity. OPSS uptake was lower among populations with greater potential for unmet need, such as individuals living in more deprived areas. Although OPSS is available to all people living within the commissioned areas, in practice not all individuals with a need for STI testing are aware of it or have the confidence and ability to access it. Differences across all socio-demographic characteristics in the relative change in testing could inadvertently increase existing inequalities in access to care and it is important to offer choice of mode of testing for service users. Funding: National Institute for Health and Care Research.