STIs
Trichomonas vaginalis PCR (swab)
PCR test for genetic material of the parasite Trichomonas vaginalis in a self-collected vaginal swab; shows a current infection.
What it measures
Trichomonas vaginalis is a single-celled parasite that is transmitted through sex and can cause inflammation of the vagina or the urethra (trichomoniasis). The PCR looks for genetic material of the parasite in material that you collect yourself with a cotton swab from deep in the vagina. In women, the infection often persists for months to years without treatment, with or without symptoms.
- A current trichomonas infection of the vagina, even if it causes no symptoms
- A possible cause of itching, more or differently smelling discharge, or a red and painful vagina
Positive
A positive result means that genetic material of Trichomonas vaginalis has been found, which fits a current infection. About half of women and most men have no symptoms from it. Trichomonas is not dangerous and can usually be cured quickly with an antibiotic; according to the LCI guideline (RIVM), more than 90 percent are cured. In pregnant women, trichomonas is associated with the waters breaking too early and premature birth. The current sexual partner(s) are also treated, even if they have no symptoms.
Negative
A negative result means that no trichomonas was found in the vaginal swab. Thuisarts advises testing without symptoms from 4 weeks after the last risk contact; within that time an infection can still be missed. This test does not measure other causes of changed discharge, such as bacterial vaginosis or a yeast infection.
If your result is abnormal
With a positive result, the GP usually prescribes an antibiotic and the current sexual partners are also treated. The LCI guideline (RIVM) also advises a full STI check and no sex until a week after treatment. Trichomonas is not notifiable.
Reliability
According to the LCI guideline (RIVM), PCR (NAAT) has replaced microscopy as the most suitable test for trichomonas, because of a higher sensitivity and specificity. On first-void urine in men and a self-collected deep vaginal swab, the sensitivity is slightly lower than on a swab taken by a doctor. The genetic material of the parasite remains detectable for 3 to 4 weeks after treatment. When the chance of trichomonas is low, such as in people without symptoms, a positive result is more often false.
Limitations
- Less than 4 weeks after the risk contact, the test can miss an infection.
- With self-collection, too little material may end up on the swab, for example if it was not inserted far enough or for too short a time; this can give a false negative result.
- A self-collected vaginal swab is slightly less sensitive than a cervical swab taken by a doctor.
- Up to 3 to 4 weeks after treatment, the test can be positive due to leftover genetic material.
How common is this
Trichomonas is uncommon in the Netherlands. In 2020, GPs made the diagnosis in about 0.3 per 1000 patients; at the Sexual Health Centers, which only test when there is a reason to, trichomonas was diagnosed in 2022 in 64 women, 11 heterosexual men and 7 men who have sex with men. It is more common in women than in men.
Who is this useful for
The result is most meaningful in women (and other people with a vagina) with symptoms such as itching, more or differently smelling discharge, or a red, painful vagina, and if a sexual partner has trichomonas. In women without symptoms, the chance of trichomonas is low.
Downsides and risks
- When testing without symptoms, if the chance of trichomonas is low, a positive result is more often false; this can lead to unnecessary treatment of you and your partner.
- Testing within 4 weeks after a risk contact can give false reassurance.
Sources
- RIVM-LCI-richtlijn Trichomonas vaginalis (2024, diagnostiek vastgesteld oktober 2024)
- NHG-Standaard Het soa-consult (M82), testindicatie trichomonas gecontroleerd via de LCI-richtlijn en Thuisarts
- Multidisciplinaire Richtlijn Seksueel overdraagbare aandoeningen (2024), module B2 Fluor vaginalis en vaginitis
- Thuisarts.nl: Ik heb trichomonas
- Thuisarts.nl: Ik wil een soa-test doen
Always discuss an abnormal result with your GP. If a result is strongly abnormal, we try to reach you as soon as possible. Read your result yourself as well and contact your GP if in doubt. A test does not make a diagnosis. Read more about risks and results