Trichomonas vaginalis is the most common nonviral sexually transmitted infection. However, because it is not a reportable disease in the United States, there is limited information on the age of infected individuals and their geographic distribution.

The purpose of this study was to evaluate the detection rates of T vaginalis infection compared with Chlamydia trachomatis by age and state in a commercial laboratory setting.

Quantitative real-time polymerase chain reactions were used to detect the presence of T vaginalis and C trachomatis in cervicovaginal samples that were obtained during gynecologic examinations. A total of 1,554,966 and 1,999,077 samples from females 10–79 years old were analyzed retrospectively for the presence of T vaginalis and C trachomatis, respectively.

The highest detection rate of an infection with T vaginalis was ages 47–53 years. For C trachomatis, the highest detection rate was ages 14–20 years. T vaginalis detection rate distribution by age shows a bimodal pattern with first peak at ages 21–22 years (4.0–4.1%) and a higher second peak at ages 48–51 years (5.4–5.8%). C trachomatis prevalence distribution by age shows a maximum peak of 8.6% at age 17 years and a rapid decline thereafter. In general, the detection rates of both pathogens were higher in the southeast and in states along the Mississippi River Valley than in other parts of the country. A nucleotide polymorphism associated with T vaginalis metronidazole resistance (ntr6_TVK80STOP) was not associated with age and was found most frequently in specimens from New Mexico and Vermont.

The detection rate of T vaginalis does not appear to decrease with age as observed for C trachomatis and reaches maximum rates in women 48–51 years old. The geographic distribution of T vaginalis appears to be broadly similar to that of other sexually transmitted diseases. The ntr6_TVK80STOP polymorphism did not have a specific association with age or geography.