Screening for Chlamydia trachomatis infection in a sexually transmitted disease clinic: comparison of diagnostic tests with clinical and historical risk factors.

Of 212 consecutive male patients and 212 consecutive female patients attending a sexually transmitted disease (STD) clinic, 36 (17%) men and 28 (13%) women had urethral or cervical cultures positive for Chlamydia trachomatis. When compared with culture, the direct fluorescent antibody test (MicroTrak, Syva Co., Palo Alto, CA) had a sensitivity of 75% and a specificity of 97% in men; for women the sensitivity and specificity were 68% and 82%, respectively. One percent of test slides from men and 11% of slides from women were uninterpretable. Designation of high-risk patients for presumptive treatment, i.e., those with suggestive clinical syndromes, gonococcal infection, or exposure to others considered at high risk for chlamydial infection, as recommended by the Centers for Disease Control, proved to be 94% sensitive, 22% specific in men, and 82% sensitive, 35% specific in women when compared with results of culture. Three different screening methods using mucopurulent cervicitis, a cervicitis score, and a series of key risk factors were less sensitive than presumptive treatment and performed worse in our study than in those published previously. Our findings suggest that use of presumptive treatment guidelines appears to be effective in directing treatment to STD clinic patients with chlamydial infection.