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New trichs for "old" dogs: prospects for expansion of Trichomonas vaginalis screening.

The urogenital protozoan Trichomonas vaginalis was first recognized nearly 2 centuries ago by the French clinician, researcher, and microscopist Donne. Since that time, roles for the protozoan's pathogenicity have been described for both females and males. Females who are symptomatic for trichomoniasis may present with vulvar irritation and a diffuse, yellow green, and malodorous vaginal discharge. Males with T. vaginalis infection can present with signs and symptoms of non-gonococcal urethritis (1). Because of the nonulcerative nature of its presentation, trichomoniasis has been characterized largely as a disease of nuisance, particularly in females. Moreover, although T. vaginalis has been recognized as the most common nonviral etiology of sexually transmitted infection (STI), [3] estimates of its prevalence have varied, largely because of inaccurate laboratory diagnostics.

Trichomoniasis is not a nationally notifiable disease in the US, and recommendations for T. vaginalis screening are not broad-ranging. The CDC states that diagnostic testing for T. vaginalis should proceed in females with vaginal discharge (1) and can be considered for females at higher risk for infection (new/multiple sexual partners, commercial sex workers, injection drug use, previous history of STI). Screening may also be indicated for HIV-positive sexually active females. However, recent data are beginning to change the outlook on trichomoniasis in the US and may eventually call for a recasting of T. vaginalis-screening recommendations. This commentary provides clinical, social, and laboratory-based rationales for expansion of T. vaginalis screening.

Approximately 50%-60% of T. vaginalis infections in women are asymptomatic (2). Mathematical modeling has projected the mean duration of T. vaginalis infection in women at 3-5 years (3). These data constitute a problematic scenario for at least 2 reasons: (a) T. vaginalis infection provides a potentially persistent and indolent conduit for subsequent sexual transmission, and (b) historical data demonstrate that approximately one-third of asymptomatic infections progress to symptomatic status within 6 months (4), requiring additional intervention and incurring increased healthcare costs.

Antecedent T. vaginalis infection affects HIV acquisition and transmission. In the US, Chesson et al. (5) estimated that 750 annual instances of new HIV infection are facilitated by T. vaginalis infection. A 2-year surveillance of >2000 African women realized a 2.57 relative risk for per-act probability of HIV transmission (P = 0.002) for women who were T. vaginalis positive at the onset of the study (6). Although metronidazole and tinidazole regimens for trichomoniasis do not cause great expense, the overall lifetime cost of treating T. vaginalis-attributable HIV infection has been estimated at $167 million (5). Analogous ramifications have been postulated for T. vaginalis and a viral etiology of much greater prevalence. Persistent human papillomavirus infection factors into the development of cervical neoplasia. Shew et al. (7) reported that the median time to clear a human papillomavirus infection was 436 days in females with concurrent T. vaginalis infection. That value was 172 days without detectable T. vaginalis.

Traditional methods for laboratory diagnosis of trichomoniasis are based on microscopical detection of motile protozoa, either directly from a primary clinical sample (wet mount) or from culture of a discharge. Attempts to mitigate ex vivo limitations of T. vaginalis culture and microscopy detection have included US Food and Drug Administration (FDA)-approved antigen detection and nucleic acid hybridization systems. These assays are approved only for analysis of female genital samples, however, and the sensitivity is inadequate for diagnosis of trichomoniasis in asymptomatic women (8). Again, this deficiency has importance with respect to disease transmission and repeat encounters with healthcare. Nye et al. (9) demonstrated increased sensitivity for noncommercial PCR detection of T. vaginalis vs. culture and wet mount analyses, and they described additional enhancement in sensitivity with transcription-mediated amplification (TMA). The enhanced diagnostic potential of TMA-based assays is partially attributable to an adjunct technology designed to remove endogenous inhibitors of amplification (10). This technology facilitates testing of first-void urine samples (9, 10) and has culminated in a commercially available assay with female genital, female urine, and gynecologic FDA indications (11).


Past studies that have used classic microscopy techniques in large part have: (a) limited T. vaginalis--detection assays to the collection of vaginal samples; (b) restricted the outlook of trichomoniasis to older women; and (c) established disease associations with concomitant Neisseria gonorrhoeae infection, geographic distribution, and African American demographics. However, the evolution of T. vaginalis nucleic acid amplification testing over the past decade has been changing previous biases pertaining to T. vaginalis detection and epidemiology.

Rates of T. vaginalis detection of 8.6% and 8.9% from vaginal and endocervical swabs, respectively (P = 0.85), were reported for 7277 females in a high-prevalence US STI community (10). The detection rate obtained with first-void urine samples was 12.6% (P = 0.0004 vs. genital swab collection). Andrea and Chapin (12) reported a >6% increase in T. vaginalis detection with urine samples, compared with endocervical or vaginal swabs. TMA-based T. vaginalis urine screening is a viable option in females for whom a pelvic examination is not indicated. Moreover, the less-invasive procurement of first-void urine samples may increase participation in T. vaginalis screening.

Studies using TMA have also associated T. vaginalis detection with older females; consequently, Andrea and Chapin (12) have espoused TMA-based T. vaginalis cotesting at the time of the annual gynecologic examination. A T. vaginalis- detection rate of >10% in women >60 years of age has been described elsewhere (10). Of greater interest were data derived from females [less than or equal to] 30 years of age. Compared with TMA-based detection of Chlamydia trachomatis, T. vaginalis was detected at increased rates in women between 21 and 30 years of age (P = 0.04; Fig. 1). In females [less than or equal to] 21 years of age, the overall rate of C. trachomatis detection exceeded that for T. vaginalis (P = 0.001); however, a subanalysis of sample source within this group revealed no significant difference between T. vaginalis- and C. trachomatis-detection rates (11.2% and 10.9%, respectively; P = 0.92) for first-void urine samples.

An analysis of data from 1086 females (13) yielded an odds ratio of 1.29 (P = 0.26) for concomitant N. gonorrhoeae detection in individuals with T. vaginalis detectable via wet mount. This odds ratio increased to 4.46 when T. vaginalis was assessed by TMA (P < 0.0001). Furthermore, the odds ratio for concomitant C. trachomatis detection was 2.34 (P < 0.0001) when TMA was used for T. vaginalis detection. Huppert et al. (14) also described significant rates of individual C. trachomatis and N. gonorrhoeae codetection with T. vaginalis in their TMA testing of 330 vaginal-swab collections.

An epidemiologic assessment of female trichomoniasis within the high-prevalence US STI community (10) revealed that 7 of the 11 ZIP Code tabulation areas that submitted the predominance of the T. vaginalis TMA requisitions had an African American majority; the other 4 areas had a largely Caucasian population. When data from the African American-majority and Caucasian-majority geographic regions were combined separately, the overall rate of T. vaginalis detection was higher in the African American-majority aggregate (P = 0.004); however, a secondary analysis of urine samples submitted from the 2 geographic aggregates noted no significant difference in detection rate (P = 0.54). These data further ascribe potential to urine samples in a broad-based trichomoniasis-screening paradigm. An extrapolation of STI phenotype data (10) also suggests the abundance of trichomoniasis in a community-wide setting. For patients presenting with at least one STI (as detected by TMA), the frequency of detecting solely T. vaginalis infection was higher in a subacute care environment (54.2% of STI-yielding encounters) than in an urban emergent care environment (40.7% of STI-yielding encounters). These data imply that widely distributed, nontraditional populations can benefit from TMA-based T. vaginalis screening.

A sampling/screening bias toward females has existed, perhaps owing to a perceived lack of testing options for males. This situation stands to change with the advent of male-urine testing with commercially available TMA in a laboratory-developed testing format (10). Epidemiology profiles (10) suggest that male trichomoniasis (albeit at a lower prevalence compared with T. vaginalis- detection rates in females) mimics that observed for females with respect to age and geographic distribution. TMA accurately detects T. vaginalis in male pharyngeal samples (10), which represents another potential use for this assay in the realm of public health. Future studies of the association of prostate carcinoma with antecedent T. vaginalis infection (15) could benefit from TMA-based screening.

Finally, Hoots et al. (16) recently recommended that trichomoniasis not be a reportable disease. That report described 4 public health importance criteria that were not sufficiently satisfied to warrant a reportable-disease status. These criteria were severity indices, associated cost, preventability, and public interest. Of these criteria, the public interest one can be rather subjective. Interestingly, Gaydos et al. (17) recently demonstrated the value of Internet recruitment for the self-collection of penile swabs to mail in for T. vaginalis screening. One can only wonder what impact additional social-media outlets may have on public interest in trichomoniasis. In the minds of some laboratory diagnosticians, the other 3 public health importance criteria will become the subjects of additional TMA-based detection and epidemiologic data. The clinical-testing experience with T. vaginalis TMA has revealed significantly increased T. vaginalis- detection rates compared with those for C. trachomatis and N. gonorrhoeae in females, statistically equivalent C. trachomatis-and T. vaginalis- detection rates for maleurine or urethral-swab collections, and an increase in test use (10).

In conclusion, the commercial availability of TMA, in an FDA-approved format for female testing and in a format adaptable to laboratory self-validation for male testing, should continue to paint a changing landscape of trichomoniasis epidemiology. As more is learned about this condition, opportunities to enhance screening recommendations will continue to present themselves. In turn, that would contribute to a more comprehensive clinical and public health assessment of T. vaginalis infection.

Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements: (a) significant contributions to the conception and design, acquisition of data, oranalysis and interpretation of data; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article.

Authors' Disclosures or Potential Conflicts ofInterest: Upon manuscript submission, all authors completed the author disclosure form. Disclosures and/or potential conflicts ofinterest:

Employment or Leadership: None declared.

Consultant or Advisory Role: None declared.

Stock Ownership: None declared.

Honoraria: E. Munson, Gen-Probe.

Research Funding: None declared.

Expert Testimony: None declared.

Patents: None declared.

Other Remuneration: E. Munson, Gen-Probe.


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Erik Munson [1,2] *

[1] Wheaton Franciscan Laboratory, Milwaukee, WI; [2] College of Health Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI.

* Address correspondence to the author at: Wheaton Franciscan Laboratory, St. Francis Hospital, 3237 South 16th St., Milwaukee, WI 53215. Fax 414-6475504; e-mail

Received August 13, 2013; accepted August 14, 2013.

DOI: 10.1373/clinchem.2013.210021

[3] Nonstandard abbreviations: STI, sexually transmitted infection; FDA, US Food and Drug Administration; TMA, transcription-mediated amplification.
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Title Annotation:Point
Author:Munson, Erik
Publication:Clinical Chemistry
Geographic Code:1USA
Date:Jan 1, 2014
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