Purulent vaginal and cervical discharge in the diagnosis of pelvic inflammatory disease.

In this structured review, we evaluated purulent vaginal and cervical discharge as diagnostic tests for pelvic inflammatory disease (PID). Using a pretest probability of PID (diagnosed clinically) of 50%, we used the odds-likelihood formulation of Bayes' theorem to calculate post-test probabilities of PID (proven by laparoscopy or endometrial biopsy). If abnormal discharge was present, the post-test probabilities of PID ranged from 50% to 73%, with a mean value of 57%. If abnormal discharge was absent, the post-test probabilities ranged from 24% to 52%, with a mean value of 39%. Therefore, the presence or absence of excess white blood cells in vaginal or cervical discharge was not particularly helpful in confirming or excluding PID in patients in whom the diagnosis was suspected from the clinical examination.