Prevalence and prediction of chlamydial cervical infection in a rural area: an UPRNet project.

BACKGROUND: Though many studies have described the prevalence of genital Chlamydia trachomatis infections in urban and suburban populations, no data on a rural general practice population have been published. Knowledge of the prevalence of infection is necessary to develop screening strategies. METHODS: The Upper Peninsula Research Network (UPRNet) is a rural primary care research group composed of five family practice offices. Cervical cultures for C trachomatis were taken on all women under the age of 36 years who presented to UPRNet physicians for a pelvic examination for any reason between August 15 and November 10, 1989. Demographic and clinical variables were analyzed for correlation with infection, and the best predictors of infection were identified by logistic regression. Previously published screening protocols were then tested on our data to develop the best predictive model for our rural population. RESULTS: C trachomatis was cultured from 25 (4.7%, 95% CI 2.9% to 6.5%) of 530 consecutive women. Infection was significantly more common among younger and single women, women with a new sex partner, and women with mucopurulent cervical discharge or increased cervical friability. No symptoms were predictive of an increased risk of infection. Based on the clinical presentation alone, the physicians correctly predicted only 28% of the infections. Using a modified Rosenthal protocol, we would have identified 80% of the infections while testing only 31% of the women. The protocols of Magder and Handsfield and their respective colleagues performed reasonably well, too. Other published screening protocols were less useful. CONCLUSIONS: The prevalence of C trachomatis cervical infection in our rural primary care office population is relatively low. In rural primary care we recommend testing all high-risk women using a modification of Rosenthal's protocol instead of relying on symptoms or clinical suspicion.