title: Chlamydia trachomatis re-infection in Spain: A STI clinic-based cohort study.
abstract: 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.
authors.affiliation: Servicio de Enfermedades Infecciosas, Hospital Universitario Basurto (OSI Bilbao-Basurto, Osakidetza), Bilbao, Spain. Electronic address: josefina.lopezdemunainlopez@osakidetza.eus.
authors.forename: Josefina
authors.initials: J
authors.lastname: López-de-Munain
authors.affiliation: Servicio de Enfermedades Infecciosas, Hospital Universitario Basurto (OSI Bilbao-Basurto, Osakidetza), Bilbao, Spain.
authors.forename: Maria Del Mar
authors.initials: MD
authors.lastname: Cámara-Pérez
authors.affiliation: Servicio de Microbiología y Control de Infección, Hospital Universitario Basurto (OSI Bilbao-Basurto, Osakidetza), Bilbao, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Imaz-Pérez
authors.affiliation: Servicio de Enfermedades Infecciosas, Hospital Universitario Basurto (OSI Bilbao-Basurto, Osakidetza), Bilbao, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Pereda-Berroeta
authors.affiliation: Servicio de Enfermedades Infecciosas, Hospital Universitario Basurto (OSI Bilbao-Basurto, Osakidetza), Bilbao, Spain.
authors.forename: Iñigo
authors.initials: I
authors.lastname: López-Azcarreta
authors.affiliation: Servicio de Enfermedades Infecciosas, Hospital Universitario Basurto (OSI Bilbao-Basurto, Osakidetza), Bilbao, Spain.
authors.forename: Josefa
authors.initials: J
authors.lastname: Muñoz-Sánchez
authors.affiliation: Servicio de Microbiología y Control de Infección, Hospital Universitario Basurto (OSI Bilbao-Basurto, Osakidetza), Bilbao, Spain.
authors.forename: Ramón
authors.initials: R
authors.lastname: Cisterna-Cáncer
authors.affiliation: Servicio de Enfermedades Infecciosas, Hospital Universitario Basurto (OSI Bilbao-Basurto, Osakidetza), Bilbao, Spain.
authors.forename: Oscar Luis
authors.initials: OL
authors.lastname: Ferrero-Beneitez
authors.affiliation: Servicio de Enfermedades Infecciosas, Hospital Universitario Basurto (OSI Bilbao-Basurto, Osakidetza), Bilbao, Spain.
authors.forename: Sofia
authors.initials: S
authors.lastname: Ibarra-Ugarte
authors.affiliation: Servicio de Enfermedades Infecciosas, Hospital Universitario Basurto (OSI Bilbao-Basurto, Osakidetza), Bilbao, Spain.
authors.forename: Zuriñe
authors.initials: Z
authors.lastname: Zubero-Sulibarria
authors.affiliation: Servicio de Enfermedades Infecciosas, Hospital Universitario Basurto (OSI Bilbao-Basurto, Osakidetza), Bilbao, Spain.
authors.forename: Josu Mirena
authors.initials: JM
authors.lastname: Baraia-Etxaburu Artetxe
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000554:Ambulatory Care Facilities; D002690:Chlamydia Infections / Q000453:epidemiology*; D002692:Chlamydia trachomatis; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012008:Recurrence; D012189:Retrospective Studies; D012749:Sexually Transmitted Diseases / Q000453:epidemiology; D013030:Spain / Q000453:epidemiology; D055815:Young Adult
keywords: Chlamydia trachomatis; Clínica de ITS; España; Factores de riesgo; Incidence; Incidencia; Re-infección; Re-infection; Recurrence; Recurrencia; Risk factors; STI clinic; Spain