ObjectivesCommonly used measures of engagement in HIV care do not take into account that the frequency of attendance is related to changes in treatment and health status. This study developed a new measure of engagement in care (EIC) incorporating clinical factors.MethodsWe conducted semi‐structured interviews with eight HIV physicians to identify factors associated with the timing of patients' next scheduled appointments. These factors informed the development of an algorithm to classify each month of follow‐up as “in care” (on or before the time of the next expected attendance) or “out of care” (after the time of the next expected attendance). The EIC algorithm was applied to data from the UK Collaborative HIV Cohort (UK CHIC) study, a large clinical cohort study.ResultsThe interviews indicated that time to next appointment varied depending on psychosocial and physical comorbidities, and clinical factors (time since diagnosis, AIDS diagnosis, treatment status, CD4 count and viral load). The resulting EIC algorithm was applied to 44 432 patients; 83.9% of the 3 021 224 person‐months were “in care”. Greater EIC was independently associated with older age, white ethnicity, HIV acquisition through sex between men, current use of antiretroviral therapy (ART), a higher nadir CD4 count, later calendar year and being seen at the clinic for the first time within the last year.ConclusionsThis algorithm describing engagement in HIV care incorporates a time‐updated measure of patients' treatment and health status. It adds to the options available for measuring this key performance indicator.

Objective: To investigate the cost-effectiveness of accelerated partner therapy (APT) compared with standard contact tracing for people with sexually transmitted chlamydia infection in the United Kingdom Design: Economic evaluation using a model consisting of two components: a population-based chlamydia transmission component, to estimate the impact of APT on chlamydia prevalence, and an economic component, to estimate the impact of APT on healthcare costs and health outcomes. Setting: United Kingdom Participants: Hypothetical heterosexual population of 50,000 men and 50,000 women aged 16-34 years. Main Outcome Measures: Cost-effectiveness based on quality-adjusted life years (QALYs) gained and major outcomes averted (MOA), defined as mild pelvic inflammatory disease (PID), severe PID, chronic pelvic pain, ectopic pregnancy, tubal factor infertility and epididymitis. Results: For a model population of 50,000 men and 50,000 women and an APT intervention lasting 5 years, the intervention cost of APT (&pound135,201) is greater than the intervention cost of standard contact tracing (&pound116,334). When the costs of complications arising from chlamydia are considered, the total cost of APT (&pound370,657) is lower than standard contact tracing (&pound379,597). Thus, APT yields a total cost saving of approximately &pound9000 and leads to 73 fewer major outcomes and 21 fewer QALYs lost. Hence, APT is the dominant PN strategy. APT remained cost-effective across the full range of sensitivity analyses. Conclusions: Based on cost-effectiveness grounds APT is likely to be recommended as an alternative to standard contact tracing for chlamydia infection in the United Kingdom