Use of spun urine to enhance detection of Trichomonas vaginalis in adolescent women

Background: Diagnosis of Trichomonas vaginalis infection is traditionally p erformed by microscopic examination of vaginal fluid. Although this techniq ue is relatively insensitive compared with culture, it is widely used becau se of its lower cost and immediate results. Objective: To assess the utility of microscopic examination of spun urine a s a means of increasing the sensitivity of microscopic diagnosis of T vagin alis. Design and Setting: Retrospective observational study performed in a hospit al-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 i ncluded, 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 uri ne for presence of motile trichomonads. Using a positive Trichomonas cultur e as the reference standard, the sensitivity of vaginal fluid alone was com pared with vaginal fluid plus spun urine. The McNemar test for paired sampl es was used to test the statistical significance of the difference in sensi tivities. 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 sensit ivity between vaginal specimen alone and vaginal specimen plus spun urine w as 12% (95% confidence interval, 3%-21%; P<.005). Nine patients who would n ot have been diagnosed by examination of vaginal fluid alone were diagnosed with the addition of spun urine examination. Conclusion: Microscopic examination of a spun urine specimen performed in c onjunction with microscopic examination of a vaginal fluid specimen improve s the detection rate of T vaginalis.