Definitions for the level of evidence (I-IV) and grade of recommendation (A-C) are provided at the end of the "Major Recommendations" field.
Recommended Tests
Microscopy of a wet mount preparation is the most commonly used diagnostic test for Trichomonas vaginalis (T. vaginalis) infection. Characteristic motile flagellated protozoa are readily seen. Microscopy for T. vaginalis should be performed as soon as possible after the sample is taken as motility diminishes with time. Wet mount microscopy is approximately 70% sensitive compared to culture in women, and significantly less sensitive in men. At present, culture techniques are still regarded as the most sensitive and specific; they provide the "gold standard" against which other methods are judged. (Evidence Level III, Grade of Recommendation B)
Culture media vary in efficiency but Diamond's TYM medium (sometimes with minor modifications) is amongst the best. Most tubes will be positive within 48 hours but should be kept for 7 to 10 days before being finally discarded. A very convenient, but expensive, way of culturing specimens is the InPouch® system which appears to be at least as sensitive as conventional tubed media. (Evidence Level III, Grade of Recommendation B)
A latex agglutination test which detects T. vaginalis antigen was described some years ago. This rapid and simple bedside test, which does not require electricity or special equipment, has been reported to have sensitivities of 95% and 98.8 % and specificities of 99% and 92.1% compared to culture for the diagnosis of T. vaginalis infection in women. This diagnostic test is available in kit form (TVlatex; Kalon Biological Ltd, Ash Vale, GU12 5QJ, UK). (Evidence Level III, Grade of Recommendation B)
More recently, several protocols have been described for the detection of T. vaginalis DNA in clinical samples using the polymerase chain reaction (PCR). Some of these assays appear to be more sensitive than culture although, as with PCR assays for Chlamydia trachomatis infection when they were first introduced, it is not immediately apparent whether samples positive by polymerase chain reaction (PCR) and negative by culture represent false negatives by culture, or false positives by PCR. No PCR assay for T. vaginalis is currently on the market in the United Kingdom (UK). (Evidence Level III, Grade of Recommendation B)
Who Should Be Tested?
Until recently, T. vaginalis has not been considered an important pathogen since, unlike other sexually transmitted infection (STIs), it was not believed to cause serious sequelae. Its importance is now being reassessed in the light of recent evidence that it is associated with adverse pregnancy outcome and facilitates the sexual transmission of HIV infection. However further research is needed to confirm these associations and to prove that the association is causal. Moreover recent trials have found that treatment of T. vaginalis infection in pregnancy does not improve pregnancy outcome, and may be harmful. Screening of asymptomatic individuals for T. vaginalis infection is therefore not currently recommended. (Evidence Levels I and II, Grade of Recommendation A)
Women attending clinics with a complaint of vaginal discharge should be tested for T. vaginalis infection. (Evidence Level III, Grade of Recommendation B) It is generally recommended that sexual partners of infected women should be treated epidemiologically. (Evidence Level 1b, Grade of Recommendation A) Testing of male partners could in theory lead to further contact tracing in those who test positive. (Evidence Level IV, Grade of Recommendation C)
Men with urethral symptoms which persist after infection with Neisseria gonorrhoeae,
Chlamydia trachomatis and Mycoplasma genitalium have been excluded or treated should be tested for T. vaginalis infection. (Evidence Level III, Grade of Recommendation B)
Test of cure is only recommended in those whose symptoms persist after treatment. (Evidence Level IV, Grade of Recommendation C)
Recommended Sites for Testing
In women, a swab should be taken from the posterior fornix at the time of speculum examination. (Evidence Level III, Grade of Recommendation B). Self-administered vaginal swabs have been used in many recent studies, and are likely to give equivalent results. (Evidence Level III, Grade of Recommendation B) First catch urine (FCU) specimens, with or without centrifugation, have also been tested in women, but the sensitivity is less than that achieved with vaginal swabs. (Evidence Level III, Grade of Recommendation B)
In men, urethral swabs or FCU samples are recommended. The sensitivity of FCU can be improved by testing a cell pellet after centrifugation. Sensitivity can be improved by testing both a swab and a FCU. (Evidence Level III, Grade of Recommendation B). Swabs from the sub-preputial space may also be tested, but this method of specimen collection has not been well validated. (Evidence Level IV, Grade of Recommendation C)
Definitions:
Levels of Evidence
Ia: Evidence obtained from meta-analysis of randomised controlled trials
Ib: Evidence obtained from at least one randomised controlled trial
IIa: Evidence obtained from at least one well designed controlled study without randomisation
IIb: Evidence obtained from at least one other type of well designed quasi-experimental study
III: Evidence obtained from well designed non-experimental descriptive studies
IV: Evidence obtained from expert committee reports or opinions and/or clinical experience of respected authorities
Grading of Recommendations
A (Evidence at level Ia or Ib)
B (Evidence at level IIa, IIb, III)
C (Evidence at level IV)
