Detailed history, physical examination, laboratory and follow-up data were obtained from 821 women coming to a primary care clinic over a two-year period with the symptoms of urinary tract (UTI) or vaginal infection. Using all available information, each patient retrospectively was given one of several mutually exclusive diagnoses. Vaginitis without UTI was diagnosed in 70% of patients, UTI without vaginitis in 12%, UTI and vaginitis in 2%. The conditional probability of the several possible diagnoses was calculated, given various combinations of clinical data; a diagnosis of vaginitis was twice as likely as a diagnosis of UTI in a patient with dysuria. On the basis of these calculations we identified efficient clinical strategies for when to perform a pelvic examination, a urinalysis, and a urine culture, and when to diagnose UTI presumptively on the basis of urinalysis.
(Arch Intern Med 138:1069-1073, 1978)