Open Access Research Sexual and testing behaviour associated with Chlamydia trachomatis infection: a cohort study in an STI clinic in Sweden Inga Veličko,1,2 Alexander Ploner,1 Pär Sparén,1 Lena Marions,3,4 Björn Herrmann,5 Sharon Kühlmann-Berenzon2 To cite: Veličko I, Ploner A, Sparén P, et al Sexual and testing behaviour associated with Chlamydia trachomatis infection: a cohort study in an STI clinic in Sweden BMJ Open 2016;6:e011312 doi:10.1136/bmjopen-2016011312 ▸ Prepublication history and additional material is available To view please visit the journal (http://dx.doi.org/ 10.1136/bmjopen-2016011312) Received 27 January 2016 Revised 16 June 2016 Accepted 26 July 2016 Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden Unit of Monitoring and Evaluation, Public Health Agency of Sweden, Stockholm, Sweden Department of Clinical Science and Education, Karolinska Institutet, Stockholm, Sweden Section of Obstetrics and Gynaecology, Stockholm South General Hospital, Stockholm, Sweden Section of Clinical Microbiology, Department of Medical Sciences, Uppsala University, Uppsala, Sweden Correspondence to Inga Veličko; inga.velicko@ki.se ABSTRACT Background: Genital chlamydia infection (chlamydia) is the most commonly reported sexually transmitted infection (STI) in Sweden To guide prevention needs, we aimed to investigate factors associated with chlamydia Methods: A cohort of visitors aged 20–40 years at an urban STI clinic in Sweden was recruited Behavioural data were collected using a self-administered questionnaire Self-sampled specimens were tested for chlamydia by a DNA amplification assay Statistically significant ( p