Risk factors for Chlamydia trachomatis infection among users of an internet-based testing service in Sweden

This study aims to assess potential risk factors for Chlamydia trachomatis infection among users of an Internet-based testing service in Sweden.

Users of an Internet-based C. trachomatis testing service sent in home urine samples by post which were analysed for C. trachomatis and answered a questionnaire regarding their socio-demographic background, sexual risk behaviour, and sexual health. Potential risk factors for C. trachomatis were determined by logistic regression models.

The questionnaire response rate was 86% (6025/6978) with a male and female response rate of 77% and 93%, respectively. 5763 subjects both answered questionnaire and supplied urine sample. Mean age was 24.4 years (range 15-67 years) and 62% were women. The participants'C. trachomatis prevalence in men was 8.0% (73/2163) and 5.6% in women (201/3600). Compared to non-infected individuals, the C. trachomatis infected men and women were younger, had a higher number of sexual partners, more intercourse without condom (only men). After adjusting for age, civil status, and geographical region, the risk factors significantly associated with C. trachomatis infection were multiple partners during the previous year, non-condom usage, and having symptoms (only men). A novel finding was that, in women, believing to be infected and having been requested to be tested by a sexual partner, was associated with an increased risk of having a C. trachomatis infection.

The Internet-based C. trachomatis testing service reaches a risk group of men and women. The results emphasise the value of self-risk assessment for C. trachomatis infection and the importance of easy accessible and simple sexual transmitted infection testing services.