ObjectivesIn Britain, sexual health clinics (SHCs) are the most common location for STI diagnosis but many people with STI risk behaviours do not attend. We estimate prevalence of SHC attendance and how this varies by sociodemographic and behavioural factors (including unsafe sex) and describe hypothetical service preferences for those reporting unsafe sex.MethodsComplex survey analyses of data from Britain’s third National Survey of Sexual Attitudes and Lifestyles, a probability survey of 15 162 people aged 16–74 years, undertaken 2010–2012.ResultsOverall, recent attendance (past year) was highest among those aged 16–24 years (16.6% men, 22.4% women), decreasing with age (<1.5% among those 45–74 years). Approximately 15% of sexually-active 16–74 year olds (n=1002 men; n=1253 women) reported ‘unsafe sex’ (condomless first sex with a new partner and/or ≥2 partners and no condom use, past year); >75% of these had not attended a SHC (past year). However, of non-attenders aged 16–44 years, 18.7% of men and 39.0% of women reported chlamydia testing (past year) with testing highest in women aged <25 years. Of those aged 16–44 years reporting unsafe sex, the majority who reported previous SHC attendance would seek STI care there, whereas the majority who had not would use general practice.ConclusionWhile most reporting unsafe sex had not attended a SHC, many, particularly younger women, had tested for chlamydia suggesting engagement with sexual health services more broadly. Effective, diverse service provision is needed to engage those at-risk and ensure that they can attend services appropriate to their needs.

IntroductionPartner notification (PN) is a process aiming to identify, test and treat the sex partners of people (index patients) with sexually transmitted infections (STIs). Accelerated partner therapy (APT) is a PN method whereby healthcare professionals assess sex partners, by telephone consultation, before giving the index patient antibiotics and STI self-sampling kits to deliver to their sex partner(s). The Limiting Undetected Sexually Transmitted infections to RedUce Morbidity programme aims to determine the effectiveness of APT in heterosexual women and men with chlamydia and determine whether APT could affectChlamydia trachomatistransmission at population level.Methods and analysisThis protocol describes a cross-over cluster randomised controlled trial of APT, offered as an additional PN method, compared with standard PN. The trial is accompanied by an economic evaluation, transmission dynamic modelling and a qualitative process evaluation involving patients, partners and healthcare professionals. Clusters are 17 sexual health clinics in areas of England and Scotland with contrasting patient demographics. We will recruit 5440 heterosexual women and men with chlamydia, aged ≥16 years.The primary outcome is the proportion of index patients testing positive forC. trachomatis12-16 weeks after the PN consultation. Secondary outcomes include: proportion of sex partners treated; cost effectiveness; model-predicted chlamydia prevalence; experiences of APT.The primary outcome analysis will be by intention-to-treat, fitting random effects logistic regression models that account for clustering of index patients within clinics and trial periods. The transmission dynamic model will be used to predict change in chlamydia prevalence following APT. The economic evaluation will use mathematical modelling outputs, taking a health service perspective. Qualitative data will be analysed using interpretative phenomenological analysis and framework analysis.Ethics and disseminationThis protocol received ethical approval from London—Chelsea Research Ethics Committee (18/LO/0773). Findings will be published with open access licences.Trial registration numberISRCTN15996256.

BackgroundWe investigated how STI risk perception relates to behavioural STI risk and STI healthcare (sexual health clinic attendance/chlamydia testing) in the British population.MethodsNatsal-3, a national probability-sample survey undertaken 2010–12, included 8397 sexually-active 16–44 year-olds. Participants rated their risk of STIs (excluding HIV) given their current sexual lifestyle. Urine from a randomly-selected sub-sample of participants (n = 4550) was tested for prevalent STIs (Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium, Trichomonas vaginalis).FindingsMost men (64% (95% CI: 62–66)) and women (73% (72–74)) rated themselves as not at all at risk of STIs, 30% (29–32) men and 23% (22–25) women self-rated as not very much, and 5% (5–6) men and 3% (3–4) women as greatly/quite a lot at risk. Although those reporting STI risk behaviours were more likely to perceive themselves as at risk, > 70% men and > 85% women classified as having had unsafe sex in the past year, and similar proportions of those with a prevalent STI, perceived themselves as not at all or not very much at risk. Increased risk perception was associated with greater STI healthcare-use (past year), although not after adjusting for sexual behaviour, indicating in a mediation analysis that risk perception was neither necessary or sufficient for seeking care Furthermore, 58% (48–67) men and 31% (22–41) women who had unsafe sex (past year) and rated themselves as greatly/quite a lot at risk had neither attended nor tested.InterpretationMany people at risk of STIs in Britain underestimated their risk, and many who correctly perceived themselves to be at risk had not recently accessed STI healthcare. Health promotion needs to address this mismatch and ensure that people access healthcare appropriate to their needs.