Background:
Genital infections with Chlamydia trachomatis (CT) continue to impact young women in San Francisco.

Objective:
To determine predictors of incident genital CT infection in young women attending community clinics in San Francisco, 2001-2003.

Method:
Fifteen to 24 year-old women were recruited from two Planned Parenthood clinics, one community college health clinic, and one adolescent health clinic. Demographic information and sexual history were obtained by interview. CT screening was performed using a urine-based nucleic acid amplification test (BD Probetec ET, BD Laboratories, Sparks, MD) both at enrollment and at a six-month follow-up.

Result:
2076 women--31% White, 22% Asian/Pacific Islander, 20% Latina, 15% African American, 12% other--had CT testing performed at baseline: 87 (4.2%) were positive; all were treated. At the six-month follow-up, 1852 women had CT testing performed and 45 (2.4%) of those tested positive. The overall incidence was 4.9 cases per 100 person-years. Seventy-nine women positive for CT at baseline returned for follow-up: 8 (10.1%) were positive a second time. However, only 18% (8/45) of women with incident infection had CT at baseline. In a multivariate model, predictors of incident infection were CT infection at baseline, age less than 20 years, African American race, and multiple sex partners in the 6 months prior to enrollment.

Conclusion:
CT incidence and re-infection rates remain elevated in young women attending community clinics in San Francisco. Prior CT infection was a significant predictor of incidence, in addition to age, African American race and increased number of partners.

Implications:
Our results underscore the need for providers to adhere to the current CDC recommendations to re-screen women 3 months following a positive CT test. Furthermore, they highlight the importance of annual screening of all sexually active young women, because 80% of incident infections were among women without a recent history of CT.