Chlamydia trachomatis re-infection in Spain: A STI clinic -based cohort study

Background: Chlamydia trachomatis (C. trachomatis) is the most frequently reported sexually transmitted infection (STI) in developed countries, but there is a lack data on its incidence and population dynamics in Spain. The objectives of this study were to estimate the incidence of C trachomatis in patients seeking medical attention in an STI clinic with a defined population catchment area, to identify factors associated with this infection, and to explore differences between factors associated with new infections and re infections. Methods: A retrospective study was conducted on a cohort of patients from a STI clinic who underwent chlamydia testing at least twice between 2007 and 2015. Results: Of the 2633 patients who met study selection criteria, 795 (30.2%) tested positive for C trachomatis at baseline (baseline Chlamydia). The overall incidence was 7.97/100 person-years (95% CI: 7.2-8.8): 5.9/100 person-years (95% CI: 5.2-6.7) among patients testing negative for C. trachomatis at baseline, and 18.3 person-years (95% CI: 15.6-21.5) among those testing positive at baseline. In multivariate analysis, the factors independently associated with overall incidence were a history of infection with C. trachomatis in the previous 6 months (hazard ratio =3.6; 95% CI: 2.3-5.4), younger age (HR < 20 vs >= 35 years =5.5; 95% CI: 3.2-9.5), male sex, 2 or more sexual partners in the previous month and year, and inconsistent condom use. Conclusions: Guidelines should be established for C. trachomatis in Spain, including recommendations on the need for follow-up and re-testing, independently of age. Though data concerning the optimal timing of re-testing are inconclusive, our findings support the establishment of a 3-6 month interval.(C) 2016 Elsevier Espana, S.L.U. and Sociedad Espanola de Enfermedades Infecciosas y Microbiologia Clinica. All rights reserved.