The chlamydia screening studies: rationale and design

Background: Screening has been recommended to reduce the prevalence and morbidity associated with genital chlamydia infection in the United Kingdom. Methods: We describe the rationale and study design of the Chlamydia Screening Studies (ClaSS), a collaborative project designed to evaluate screening outside genitourinary medicine clinics. A nonselective, active screening approach in 16-39 year olds randomly sampled from 27 general practice lists in the Bristol and Birmingham areas formed the basis of interlinked studies: a case-control study was used to investigate factors to improve the targeting of screening; participants with chlamydia were invited to enrol in a randomised controlled trial to evaluate partner notification conducted in primary care; and laboratory based studies were used to assess the best specimens and tests. We also explored psychosocial effects of screening and partner notification and modelled the cost effectiveness of the programme. Conclusion: Results from four pilot practices show that mailing of specimens for chlamydia testing is feasible but that it is difficult to achieve high response rates with postal screening. The high prevalence of asymptomatic infection in men suggests that efforts to screen men for chlamydia should be strengthened.