Factors affecting the performance of smear and culture tests for the detection of Neisseria gonorrhoeae.

The probability of gonorrhea in men attending the DeKalb County, Georgia, clinic for sexually transmitted diseases with the chief complaint of urethral discharge and/or dysuria and whose urethral smears contain intracellular gram-negative diplococci is 94.8%. Absence of intracellular gram-negative diplococci from smears of the same men in associated with a 92.6% probability that they have nongonococcal urethritis rather than gonorrhea. There is a 97.3% probability of gonorrhea in our female patients at high risk of being infected and whose cervical smears contain intracellular gram-negative diplococci. Absence of intracellular gram-negative diplococci is associated with a probability of only 51.2% that these women do not have gonorrhea. The probability of gonorrhea in our male patients, whose smears contain intracellular gram-negative diplococci, drops from 94.8% to 34.9% when specimens are obtained from sexually active men without urethritis and to 53.9% when an inexperienced technician interprets smears from patients with urethritis. Vancomycin . HCl, which is included in Neisseria gonorrhoeae--selective media for suppression of microbial contaminants, also inhibited 2.4% of our gonococcal isolates and resulted in a falsely negative test. Awareness of these and other limitations of tests for gonorrhea, and of the magnitude and means of control of these limitations is essential to determining the presence or absence of gonococcal disease.