The utility of wet prep in predicting Neisseria gonorrhoeae and Chlamydia trachomatis

Diagnosing Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) cervical infections can be difficult in the Emergency Department without real-time testing, as historical and physical elements are known to be unreliable.

To evaluate the utility of the vaginal wet mount preparation (wet prep) in predicting an infection with NG or CT.

A retrospective chart review was performed on 12 months of data from September 2007 to August 2008 on patients aged 18 years and above who had a chief complaint requiring a pelvic examination and had concurrent testing for NG/CT and a wet prep. Wet preps were analyzed and reported as quantity of white cells and clue cells present (none, few, moderate, or many) as well as the presence of Trichomonas vaginalis (TV). Wet prep results were evaluated to see if there was a correlation with NG/CT.

There were 2439 patient encounters reviewed. A total of 373/2439 (15.3%) patient encounters were positive for NG or CT; 272/2439 (11.2%) were positive for TV, whereas 966/2439 (39.6%) had white cells and 995/2439 (40.8%) had clue cells on wet prep. Clue cells and TV did not correlate with the presence of NG or CT. Only the presence of "moderate" and "many" white cells correlated with NG or CT (odds ratio [OR] 1.58, 95% confidence interval [CI] 1.12-2.22 and OR 2.47, 95% CI 1.86-3.27, respectively).

In patients who are diagnosed with NG or CT, the presence of TV or clue cells on wet prep is an unreliable marker for diagnosis. However, having moderate or many white cells present on wet prep does increase the probability of concurrent NG or CT infection and may be used in cases where the clinical suspicion is equivocal.