BACKGROUND: Diagnosis of Trichomonas vaginalis infection is traditionally performed by microscopic examination of vaginal fluid. Although this technique is relatively insensitive compared with culture, it is widely used because of its lower cost and immediate results.

OBJECTIVE: To assess the utility of microscopic examination of spun urine as a means of increasing the sensitivity of microscopic diagnosis of T. vaginalis.

DESIGN AND SETTING: Retrospective observational study performed in a hospital-based adolescent clinic.

SUBJECTS: Female patients enrolled between July 1995 and August 1996 into a larger study evaluating diagnosis of vaginal infections (N = 686). To be included, subjects had to have a positive culture for T. vaginalis (n = 97); those who did not have a spun urine examination were excluded (n = 22).

MAIN OUTCOME MEASURE: Microscopic examination of vaginal fluid and spun urine for presence of motile trichomonads. Using a positive Trichomonas culture as the reference standard, the sensitivity of vaginal fluid alone was compared with vaginal fluid plus spun urine. The McNemar test for paired samples was used to test the statistical significance of the difference in sensitivities.

RESULTS: Ninety-seven subjects had culture results positive for Trichomonas. Of these, 75 (77%) had a spun urine examination performed. Subjects were aged 13 to 22 years and all were African American. Seventy-three percent of the infections were detected by vaginal fluid specimen, 64% by spun urine, and 85% by either vaginal specimen or spun urine. The difference in sensitivity between vaginal specimen alone and vaginal specimen plus spun urine was 12% (95% confidence interval, 3%-21%; P

CONCLUSION: Microscopic examination of a spun urine specimen performed in conjunction with microscopic examination of a vaginal fluid specimen improves the detection rate of T. vaginalis.