Variability of HIV/STI testing coverage and preferences as differentiated by age, sex and risk behaviours – a prospective population-based study in Hong Kong, 2021–2023

Background To achieve the World Health Organization’s 2030 targets for public health control of HIV and sexually transmitted infections (STIs), high testing coverage of the population at risk is important. This study aims to profile the HIV/STI testing patterns and preference in the general population to inform strategy development. Methods This is a prospective study on sexually experienced individuals in Hong Kong recruited by geographically clustered random sampling, with baseline (2021–2022) and one-year follow-up (2022–2023) online surveys and free self-sampled testing for STI. Factors associated with testing history were examined in multivariable logistic regression. Results Among 1,112 heterosexual adults (680 female and 432 male), some 73% females and 75% males were sexually active in the past one year, with higher proportion of female aged 18–24 (28%) and male aged 18–24, 40–49 and 60–69 (> 30%) reporting higher-risk sexual behaviours (defined as any concurrent sexual partnership, commercial sex, and/or > 4 sex partners in the past one year). Around 10% of participants reported history of STI diagnoses (including genital warts, chlamydia and gonorrhoea), 89% of which occurred > 2 years ago. Only 40% of individuals with higher-risk sexual behaviour had ever tested for HIV/STI, which was even lower in older adults. Younger age and male were significantly more likely to have undergone HIV test than older adults and female, but there was no difference regarding STI testing. Above half were unaware of HIV and STI testing venues. Cost and privacy were common factors affecting testing decisions, the proportion of which varied by age groups. Testing in physical venues with healthcare professionals was preferred by older adults, but non-governmental organisations and online test kits were preferred by younger adults. Some 40% of participants who were at higher-risk but never tested for STI had submitted their samples for STI testing at baseline and/or follow-up. Conclusions The HIV/STI testing coverage of people with higher-risk sexual behaviours in the population was low. Testing intention and service preference varied by age, suggesting different testing services are needed to scale up testing. Use of self-sampled STI testing could capture additional higher-risk never testers.