Retesting for genital Chlamydia trachomatis among visitors of a sexually transmitted infections clinic: randomized intervention trial of home- versus clinic-based recall

Background: Reinfections of Chlamydia trachomatis (Ct) are common. In a two-armed intervention study at an urban STI clinic in the Netherlands, heterosexual Ct-positive visitors received an invitation for retesting after 4-5 months. Interventions were either home-based sampling by mailed test-kit, or clinic-based testing without appointment. Methods: Data collection included socio-demographic and sexual behavioural variables at first (T0) and repeat test (T1). Participation in retesting, prevalence and determinants of repeat infection among study participants are described and compared with findings from non-participants. Results: Of the 216 visitors enrolled in the study, 75 accepted retesting (35%). The retest participation was 46% (50/109) in the home group versus 23% (25/107) in the clinic group (p = 0.001). Men were less often retested than women (15% versus 43%, p < 0.001). The overall chlamydia positivity rate at retest was 17.3% (13/75) compared to 12.4% seen at all visits at the STI clinic in 2011. Repeated infections were more frequent among non-Dutch than Dutch participants (27.0% versus 7.9%; p = 0.04) and in persons reporting symptoms (31.0% versus 7.0%; p = 0.01). Both untreated infections of current partners as well as unprotected sex with new partners contribute to repeated infections. Conclusion: The high rate of repeated infections indicates the need for interventions to increase retesting; improvement of partner-management and risk reduction counselling remain necessary. Home-based testing was more effective than clinic-based testing. However other strategies, including self-triage of patients, may also increase repeat testing rates and personal preferences should be taken into account.