Clinical utility of measuring white blood cells on vaginal wet mount and endocervical Gram stain for the prediction of chlamydial and gonococcal infections

Background: White blood cells on endocervical Gram stain and vaginal wet mo unt are frequently used to predict chlamydial and gonococcal infections. Pr evious studies provide conflicting evidence for the clinical utility of the se tests. Goal: To evaluate the clinical utility of measuring white blood cells on va ginal wet mount and endocervical Gram stain for the prediction of chlamydia l infection and gonorrhea. Study Design: Women undergoing pelvic examinations at 10 county health depa rtment family planning and sexually transmitted disease clinics were tested for chlamydial infection by ligase chain reaction assay (n = 4550) and for gonorrhea by culture (n = 4402). Vaginal wet mount and endocervical Gram s tains were performed in county laboratories at the time of examination. Results: The prevalences of chlamydial infection and gonorrhea were 8.8% an d 3.2%, respectively. For detection of chlamydial or gonococcal infection, the likelihood ratio was 2.85 (95% CI, 2.10-3.87) for > 30 white blood cell s on vaginal wet mount and 2.91 (95% CI, 2.07-4.09) for > 30 white blood ce lls on endocervical Gram stain. Similar results were seen for individual di agnoses either of chlamydial infection or of gonorrhea, Conclusion: Vaginal wet mount and endocervical Gram stain white blood cells are useful for the presumptive diagnosis of chlamydial infection or gonorr hea only in settings with a relatively high prevalence of infection or when other predictors can increase the likelihood of infection.