Background Prevalence and risk data concerning Chlamydia trachomatis CT in Italy is scare. We present a study of the prevalence and predictive risk factors for CT infection by comparing two different female populations at risk because of age (18–26) but with different socio-cultural backgrounds.

Methods An anonymous questionnaire concerning sexual behaviour was given to 493 female medical students aged 18–26 at the University of Torino and to women aged 18-26 attending three Family Planning Clinics (FPC) in Asti, Italy. A first-catch urine sample was collected into a liquid transport medium (UPT, Becton Dickinson) from each subject who completed the questionnaire. Nucleic acid amplification testing for CT was performed using the BD ProbeTec ET assay. Age and behavioural characteristics were compared.

Results 6 women of 493 medical students tested (1.22%) were positive for CT, while 11 of 262 women attending FPC had a positive CT result (4.2%) (χ²=5.7; p=0.017). Different behaviours between the female medical students and the FPC population respectively for non-barrier contraceptive methods were: (34% vs 59%); age <18 at first intercourse (40% vs 60%); more than 1 partner during last year (16% vs 20%), or the last 5 years (2% vs 56%). Risk of infection was associated with >4 partners during the last 5 years both in medical students and to a lesser extent in women attending FPC (OR 10.7; CI 2 to 49 and, respectively (OR 3.7; CI 1.2 to 12). Age at first intercourse was also a factor. Women in FPC whose age was <18 at first intercourse were at higher risk of CT (OR 7.6; CI 1.1 to 30) than the female medical students (OR 1.5; CI 0.3 to 8). Logistic regression confirmed that >4 partners during the last 5 years in both groups (Wald 7.3; p<0.01 [students]; 3.7 p<0.05 [FPC subjects]) and an age <18 at first intercourse only in FPC subjects (Wald 3.5; p<0.06) were independent predictors of infection.

Conclusions Female medical students showed a significantly lower prevalence of CT compared to the female population of same age but different socioeconomic background. The number of partners in the last 5 years and age at first intercourse were the factors regarding this difference. Awareness and the level of knowledge, possibly dependent on cultural factors, seem to reduce the prevalence. The importance of targeted CT screening programs to groups at greatest risk, while promoting widespread educational efforts and awareness of risk among general population is apparent.