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range from 69 to 75% with specimens from women.
However, Reported specificities of in-house PCR assays for T. vaginalis detection
because positive cultures may result from the growth of even a few range from 88 to 100%.
One NAAT that uses transcription-
trichomonads in a clinical specimen, this method is more sensitive than mediated amplification (APTIMA TV analyte-specific reagents; Gen-Probe,
wet-mount microscopy and substantially improves detection of T. vaginalis. Inc., San Diego, CA) is now commercially available but has not yet been
Vaginal swab specimens transported in Amies gel transport tubes maintain evaluated for clearance by the US Food and Drug Adminstration (FDA).
T. vaginalis viability for up to 24 hours prior to inoculation into culture Validation studies comparing the APTIMA TV assay with in-house PCRs
Trichomonads from vaginal swab specimens have been shown to and traditional methods for detection of T. vaginalis from women report
remain viable in a small amount of saline for up to 20 minutes prior sensitivity ranges from 96 to 98% and specificity of 98%.
to culture inoculation.
A combined approach of microscopy followed by
culture if the wet-mount is negative can increase diagnostic sensitivity in Vaginal swabs are generally more sensitive specimens than urine for
women over microscopy alone.
T. vaginalis culture is less sensitive for NAAT detection of T. vaginalis infections in women.
detection of trichomoniasis in men.
Furthermore, cultures inoculated trichomonads primarily infect the vagina, T. vaginalis can also be detected
with specimens from men should be incubated and examined daily for the in endocervical swabs using NAAT.
For diagnosis in men, NAAT appears
full five days, since they often do not become positive until after three or to be more sensitive with urine than with urethral swabs.
more days of incubation.
Although culture of T. vaginalis in men is for NAAT detection of T. vaginalis in men, just as for culture, testing
preferred over wet-mount microscopy for diagnosis, the optimal specimen multiple specimens will substantially increase the number of cases
for culture is not clear. Studies indicate that sampling multiple urogenital identified. Highly sensitive and specific NAATs are particularly important
sites substantially increases the detection of T. vaginalis in men.
for the diagnosis of T. vaginalis infection in men, since traditional
Semen cultures have been shown to be valuable for documentation of microscopy and culture perform so poorly with specimens from men. In
infection; infections may be diagnosed by positive semen cultures in the studies of men attending US STD clinics, T. vaginalis infection was
face of concomitant negative cultures from urine, urethral swabs or detected by culture in 3–5% of men compared with 12–17% using
However, collection of semen for diagnostic purposes PCR.
In a study conducted in Malawi, in southeastern Africa, the
is not feasible in most clinics, and microscopic examination of more than addition of urethral swab PCR to wet-mount microscopy and urethral
one specimen per subject is time-consuming. A practical approach is to culture increased T. vaginalis detection from 16 to 21% in symptomatic
combine a urethral swab specimen with a first-voided urine sediment in a men attending an STD clinic and from 9 to 12% in asymptomatic men
attending a dermatology clinic compared with wet-mount and culture
Just as is the case for NAATs used to detect gonorrhea and
Rapid Diagnostic Tests chlamydial infection, detection of T. vaginalis nucleic acid does not
Point-of-care tests for diagnosis of trichomoniasis in women are now require the presence of viable organisms. This feature provides a distinct
commercially available, and they provide rapid and sensitive detection advantage when prolonged specimen storage and/or transport to the
methods during the same clinic visit. Unfortunately, no rapid diagnostic laboratory prohibit the use of T. vaginalis culture. In addition, the superb
tests are yet available for diagnosis of trichomoniasis in men. The Affirm™ sensitivity of NAATs for a number of sexually transmitted pathogens
VPIII Microbial Identification Test (Becton Dickinson, Franklin Lakes, NJ) is allows the use of convenient, non-invasive specimens such as urine or
an office-based oligonucleotide probe test that has a sensitivity of self-obtained vaginal swabs, which may contain fewer organisms than
80–90% and a specificity of 95% compared with wet-mount plus culture semen or urethral swabs from men or clinician-collected vaginal swabs
using vaginal swabs.
Trichomonas Rapid Test (Genzyme from women. However, consumers of NAAT results must also be mindful
Diagnostics, Cambridge, MA) is an immunochromatographic strip test that that these tests may remain positive for some time after treatment;
detects T. vaginalis antigens in vaginal swabs. Performance characteristics although organisms have been killed, they may not be completely cleared
of the OSOM test (sensitivity 83–90% and specificity 99–100%)
are from the genito-urinary tract immediately after treatment. Studies
superior to wet-mount microscopy and compare favourably with culture examining clearance of N. gonorrhoeae and C. trachomatis nucleic acids
and nucleic acid amplification testing (NAAT) (described below). Rapid indicate that negative NAAT results can be expected one to two weeks
tests are likely to be particularly important for use in settings where following successful antimicrobial therapy.
Similar kinetics are likely
culture and microscopy are not possible, and in populations such as for T. vaginalis, but it will be important to establish the specific timeframe
adolescents and patients who are seen in emergency departments, both for clearance of trichomonad nucleic acids with newly developed
of whom present challenges to follow-up. diagnostic tests.
Nucleic Acid Amplification Tests Improving Diagnosis and Management of Trichomoniasis
The development of highly sensitive NAATs for detection of T. vaginalis Perhaps the biggest obstacles to control of trichomoniasis are the lack of
has lagged behind diagnostic advances for detection of Neisseria routine screening or testing for T. vaginalis infection in both male and
gonorrhoeae and Chlamydia trachomatis. Until recently, in-house female patients receiving care in various clinics, and the limited access to
polymerase chain reaction (PCR) assays were the only available NAATs, newer, more sensitive detection methods. In light of the high prevalence of
and access has been limited primarily to research laboratories. The trichomoniasis among HIV-negative and HIV-positive persons and the
performance of various PCR primers assessed in clinical studies differs, potential complications of untreated infections including pelvic
with reported sensitivities ranging from 80 to 100%.
Special inflammatory disease and adverse pregnancy outcomes, screening for
challenges arise in evaluating the specificity of NAATs, since the reference T. vaginalis among asymptomatic at-risk patients should be strongly
standard (usually culture) is often inherently less sensitive than the newer considered. Improved diagnosis of trichomoniasis involving infected patients
amplification tests. As a result, some positive NAAT results classified as and their sexual partners is needed as treatment with metronidazole 2gm or
false-positives in comparative analyses are likely to be true positives.
tinidazole 2gm orally in single doses is easy and highly effective.
In a recent
40 EUROPEAN GENITO-URINARY DISEASE 2007