Am Fam Physician. 2000;61(8):2476-2479
Trichomoniasis is a common sexually transmitted disease. In the United States, an estimated 6 million men and women are infected with Trichomonas vaginalis annually. Common symptoms of T. vaginalis infection in women include vaginal itching, irritation and dysuria; however, up to 50 percent of these infections are asymptomatic. Trichomoniasis is usually diagnosed by wet mount microscopy, which has an average sensitivity of 60 to 80 percent for detection of the motile T. vaginalis organisms. Culture of T. vaginalis using a Diamond medium, which has a sensitivity of 91 to 100 percent, is considered to be far superior to wet mount examination. However, the culture technique is more expensive than wet mount examination and requires two to seven days to obtain results. Because trichomonads are sometimes noted during routine examination of a spun urine specimen, Blake and colleagues performed a retrospective analysis to determine if the use of a spun urine specimen improves the rate of detection of T. vaginalis when combined with a routine examination of vaginal fluid.
The study included females between 12 and 22 years of age who were seen at an adolescent clinic in an urban setting. The participants were part of a larger study that was evaluating the diagnosis of vaginal infections. Data for all patients found to have a culture positive for T. vaginalis were retrospectively reviewed. For purposes of the study, a positive Trichomonas culture was considered the reference standard. All eligible patients had a wet mount examination of vaginal fluid by microscopy for motile organisms. In addition, for each of these patients a centrifuged spun urine specimen was examined by microscope at ×400 power. A laboratory technician performed both diagnostic studies.
Ninety-seven patients had a culture positive for T. vaginalis; 75 of these also had a spun urinalysis. Of the 75 patients included in the analysis, 55 had a positive culture on vaginal wet mount, 48 had a positive culture on spun urine examination and 64 had a culture positive for T. vaginalis on both tests. Nine patients who had negative vaginal wet mount results were diagnosed with T. vaginalis infection by the urine specimens. Collectively, however, the spun urine examination was less sensitive compared with vaginal fluid testing. After a sensitivity analysis of the data was performed, it was determined that the combination of the microscopic tests resulted in detection of 12 percent more T. vaginalis infections than the wet mount examination alone.
The authors conclude that adding a spun urine specimen to a routine wet mount examination of vaginal fluid improves the rate of detection of T. vaginalis. Because T. vaginalis can infect the urethra as well as the vagina, urine is a logical source for examination, especially in women who are being examined for vaginal problems.