A new diagnostic index for predicting cervical infection with either Chlamydia trachomatis or Neisseria gonorrhoeae

To develop and test a diagnostic index for estimating the probability of cervical infection with either Chlamydia trachomatis or Neisseria gonorrhoeae.

Prospective, cross-sectional study in two phases: 1) to develop a diagnostic index based on independent predictors of cervical infection; 2) to test the index.

A hospital-based clinic and a student health service.

Development phase: 190 nonpregnant women seen in the gynecology clinic; testing phase: 588 women seen in the gynecology clinic (n = 372) or the student health service (n = 216).

Experienced clinicians recorded historical, physical, and microscopic findings on standard forms and tested women for chlamydial and gonococcal infections.

Three independent predictors of cervical infection were identified and weighted: age (two points if less than 20 years and one point if 20-29 years); a new sex partner or one suspected of having a genital infection (one point); purulent vaginal discharge (one point). In the testing groups, cervical infection was present in none of 62 women with no points, seven of 269 (3%) with one point, 14 of 188 (7%) with two points, and 19 of 69 (28%) with three or four points (p less than 0.001). The index estimated the probability of infection more accurately (p less than 0.01) than did clinicians, performed well in each site, and remained accurate when C. trachomatis and N. gonorrhoeae were considered separately.

The diagnostic index accurately estimates the probability of cervical infection with either C. trachomatis or N. gonorrhoeae and may be useful in selecting women for definitive diagnostic testing.