Update on Laboratory Diagnosis and Epidemiology of Trichomonas vaginalis: You Can Teach an “Old” Dog “New” Trichs
Introduction
The French microscopist, clinician, and researcher A. F. Donné discovered the protozoan T. vaginalis 180 years ago. Trichomoniasis, the clinical entity ascribed to the pathogen, has become the most prevalent non-viral sexually transmitted infection (STI) in the United States (Fig. 1). A surveillance study conducted by the U.S. Centers for Disease Control and Prevention (CDC) in 2008 estimated trichomoniasis prevalence in this country at 4 million cases, with approximately 1 million new cases of T. vaginalis infection being diagnosed annually [1]. As will be posited and further described throughout this review, several factors impact the true characterization of trichomoniasis. As an introductory example, T. vaginalis prevalence rates are rather disparate on a worldwide basis. In contrast to reports of >20% prevalence in some U.S., African, and indigenous Australian population centers [2, 3, 4, 5], a number of European, Asian-Pacific, and non-indigenous Australian studies have documented rates lower than 5% [6, 7, 8, 9, 10].
The advent of molecular-based laboratory detection of T. vaginalis has broadened our knowledge of trichomoniasis, allowing new perspectives on disease epidemiology and opportunities for prevention. In addition, advancements related to diagnostic algorithms have garnered much attention in the clinical research setting. A PubMed primary literature search (U.S. National Library of Medicine and the National Institutes of Health) conducted in February 2016 using the search parameter “Trichomonas vaginalis” filtered by the possibility of “antigen,” “molecular testing,” “nucleic acid hybridization,” “PCR,” “nucleic acid amplification testing,” “LAMP” (loop-mediated isothermal amplification), or “transcription-mediated amplification” selected 629 primary citations from the years 1964 to 2016, with over 25% published since the beginning of 2012. This brief commentary, with focus largely on literature published within the past 3 years, discusses updates on T. vaginalis epidemiology and laboratory testing.
Section snippets
Females
Trichomoniasis can be characterized by a diffuse, malodorous, yellow-green vaginal discharge with vulvar irritation [11]. While pruritis and dysuria may be present, a majority of T. vaginalis infections are actually thought to be asymptomatic. This has long been a source of consternation for clinicians and researchers in the context of proper laboratory diagnostic strategies and clinical management. Data published nearly 25 years ago stated that approximately one-third of patients with
Non-molecular modalities
The success of non-molecular means of T. vaginalis detection is largely depenent on the organism burden or disease prevalence. Wet-mount analysis involves collection of a vaginal swab, placement of the swab into physiologic saline (vaginal saline suspension), followed by microscopic observation of the suspension for motile flagellates using a high-power objective. This technique may have its best application in remote and underserved locales that may also experience financial constraints. In a
Conclusion
Evaluation of reports regarding past modalities for diagnosis of trichomoniasis is compromised by an evolving molecular reference standard. This is further confounded by analytical sensitivity differences between DNA and RNA amplification methods demonstrated both in vitro and in the clinical setting. However, these recently commercialized, highly accurate diagnostic modalities, particularly those based on TMA, are facilitating “new” outlooks on the “old” epidemiology of trichomoniasis. This
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Update in the Molecular Diagnostics of Sexually Transmitted Infections
2019, Physician Assistant ClinicsCitation Excerpt :However, recent data have demonstrated that T vaginalis antigen testing yields greater accuracy in high-prevalence populations, irrespective of patient symptoms.72 Sensitivity values of the aforementioned methods, in addition to methods involving nucleic acid hybridization, have decreased with the emergence of NAAT.63 Within a population of 5% T vaginalis prevalence, Andrea and Chapin73 reported 63.4% sensitivity of commercial nucleic acid hybridization compared with a NAAT reference; 46.3% sensitivity of nucleic acid hybridization compared with NAAT was observed in a population exhibiting 16.9% T vaginalis prevalence.74
Clinical laboratory assessments for Mycoplasma genitalium in a high-prevalence sexually-transmitted infection community reveal epidemiologic dichotomies with Trichomonas vaginalis
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