Chlamydia trachomatis among Youth - Testing Behaviour and Incidence of Repeat Testing in Stockholm County, Sweden 2010-2012

BACKGROUND Widespread testing and screening for genital Chlamydia trachomatis is often advocated as an important method to halt the epidemic. Sweden has long tradition of opportunistic screening services. Nevertheless infections rates have continued to rise over the past two decades, despite increased access to testing and treatment services. METHODS In this retrospective cohort study we describe the testing behavior for genital Chlamydia trachomatis among youth in Stockholm County, with a focus on repeated testing. Specifically we (a) study positivity rates among single and repeat testers, we (b) estimate the incidence of repeat testing and the rates of infection in repeat testing episodes, and we (c) estimate time to repeat testing and factors associated with repeat testing. All youth (aged ≥12 and <26) that tested for Chlamydia trachomatis in one of 33 Youth Health Clinics in Stockholm County between 1 January 2010 and 31 December 2012 were included in the study. RESULTS The cohort comprised a total of 65,951 individuals who did 119,699 tests during the study period. 42% of youth were repeat testers, the incidence of repeat testing was 35.0/100 person years. The overall baseline prevalence was 7.9%. Positivity rates of baseline tests among repeat testers were nearly twice as high among single testers of either sex. These were 17.1% and 9.8% among male repeat and single testers respectively. The corresponding rates for women were 9.4% and 4.3%. Positivity rates among repeat tests did not decline compared to the overall baseline positivity. Baseline test result and sex significantly influenced the occurrence of repeat testing. CONCLUSION Among repeat testers we found high rates of Chlamydia trachomatis both at baseline and at repeat tests which suggests the possibility that this group might be continuing to engage in unsafe sexual practices. Given the extent of repeat testing and the high positivity rates on repeat testing, further research among this group is required to inquire into reasons for repeated testing.