Genital infection by Chlamydia trachomatis in Lisbon:: prevalence and risk markers

Background. There is little information about the prevalence and risk markers for Chlamydia trachomatis infections in Portugal. Objectives. Our aim was to assess the prevalence of C. trachomatis genital infection and to study variables associated with this infection in a group of sexually active women aged less than or equal to30 years living in the Lisbon area and to estimate the prevalence of C. trachomatis infection among partners of infected patients. Methods. A systematic sample of women observed in general practice family planning and teenager clinics was collected. A questionnaire was administered, followed by a pelvic examination. A first-catch urine sample was taken for polymerase chain reaction (PCR) Amplicor assay. When a sample tested positive, the woman was invited to obtain a urine sample from her partner. Socio-demograhic, behavioural and clinical variables were studied and their association with the PCR Amplicor result was assessed. Results. A total of 1108 women, aged between 14 and 30 years, were studied. Fifty-one women (4.6% of total sample) tested positive for C. trachomatis. The prevalence of infection was slightly higher in patients aged less than or equal to19 years (5.3%) than in age groups 20-25 (4.8%) and 26-30 years (3.9%). African ethnicity was related to a higher percentage of infection than European ethnicity: 9.8% versus 3.8%, P= 0.0067. Use of condoms 'sometimes/never' was associated with a higher prevalence of infection: 5.2% versus 2.3% in those responding 'always/almost always' (P= 0.0447). An altered cervix was associated with a higher prevalence of infection: 7.3% versus 3.7% with a normal cervix (P= 0.0106). Urine samples were obtained from 16 partners of infected patients. Six partners (37.5%) tested positive for C. trachomatis. Conclusions. A 4.6% prevalence of C. trachomatis genital infection was found. African ethnicity, using condoms 'sometimes/never' and an altered cervix were associated with C. trachomatis infection, but showed low positive predictive value for C. trachomatis infection. Younger age may be associated with a slight increase in risk. Contact tracing for diagnosis and treatment remains a difficult issue to approach effectively.