PathAdvantage | 04/11/2014In the US, Trichomonas vaginalis (TV) infections are not reportable to state agencies and therefore actual prevalence data is limited. In addition, as many as 85% of infected women1 are asymptomatic and therefore do not even undergo testing. Also, in those that are tested, the sensitivity of diagnostic tests varies widely, as shown below:
- Nucleic Acid Amplified Tests demonstrate a sensitivity of 100%.
- Cell culture (which was the gold standard, prior to NAAT) ranges in sensitivity from 50-80%.
- BD Affirm TM VPIII Direct Probe Test (a non-amplified test) has a sensitivity of 63.4%.
- Wet mount averages 54%. (In addition, survival of TV declines precipitously over time on wet mount, making motility more difficult to assess.)
- Papanicolaou smear rates lowest, at 24%.
Infection with TV in women is also often under- estimated in terms of morbidity. Pelvic inflammatory disease, preterm birth and infertility are well described; the below associations are less widely known, however.
- Increased incidence of infection with HSV type 22
- Increased chance of HIV acquisition and transmission3
- Increased risk for cervical intraepithelial neoplasia4 (possibly due to the increased time to clear HPV in TV infected females)
- The link between maternal infection with TV and intellectual disability in children (see additional article in this issue.)
Few studies examine the prevalence of TV across age groups, and many are limited by the diagnostic tests previously described. A recent study5 used real-time PCR assays and compared by age groups the rates of T. vaginalis, C. trachomatis and N. gonorrhea in Florida, Texas and New Jersey. The results for Texas are below; TABLE 1 shows prevalence across the entire study population for all three organisms, while TABLE 2 shows the distribution of T. vaginalis across various age groups in Texas. 
An overall infection rate of 4.3% with TV was noted in women aged 12-75. Of note is the highest rate of infection in the 46-55 year age group. The similarity in prevalence to C. trachomatis is striking, as is the much greater prevalence over that of N. gonorrhea. The latter pathogens are usually both tested for due to co-infection; perhaps it is time for a ‘triple screen’?
BIBLIOGRAPHY 1 The prevalence of Trichomonas vaginalis in the United States, 2001-2002. Sutton MY, Sternberg M, Kouman E, McQuillan G, Berman S, Markowitz L. 2006, Obstet Gynecol, p. 107. 2 Incidence of herpes simplex virus type 2 infection in 5 STD clinics and the effect of HIV/STD risk-reduction counseling. Gottlieb SL, Douglas JM, Foster M, Schmid DS, Newman DR, Bolan A. 2004, J Infect Dis, pp. 1059-67. 3 Trichomonas vaginalis, HIV and African- American. Sorvillo F, Smith L, Kerndt P, Ash L. 2002, Emerg Infect Dis, p. 749. 4 Trichomonas vaginalis and human papillomavirus infection and the incidence of CIN grade III. Gram IT, Macaluso M, Churchill J, Stalsberg H. 1992, Cancer Causes Control, pp. 231-6. 5 Detection Rates of Trichomonas vaginalis in Different Age Groups, Using Real-Time Polymerase Chain Reaction. Stemmer SM, Adelson ME, Trama JP, Dorak MT, Mordechai E. 2012, Journal of Lower Genital Tract Disease, pp. 352-357. REFERENCES: Available upon request