Explanation

Trichomonas vaginalis PCR (urine): what is measured?

Trichomonas vaginalis is a single-celled parasite that is transmitted through sex and can cause inflammation of the urethra or the vagina (trichomoniasis). The PCR looks for genetic material of the parasite in the first portion of urine; that is why you only catch the first part of the stream and, according to the kit instructions, do not urinate for at least 1 hour beforehand. According to the LCI guideline (RIVM), in men the infection causes no symptoms in about 9 out of 10 cases and often clears up on its own.

What can it detect?

A current trichomonas infection of the urethra, even if it causes no symptoms
A possible cause of urethral symptoms in men that last longer than 4 weeks while chlamydia and gonorrhea have been ruled out

Result

What does the result mean?

Positive result

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 result

A negative result means that no trichomonas was found in the urine. Thuisarts advises testing without symptoms from 4 weeks after the last risk contact; within that time an infection can still be missed. Urine is slightly less sensitive than a urethral swab, so with persistent symptoms the doctor may do other tests.

After an abnormal result

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

How reliable is the test?

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.

What can affect the result?

Less than 4 weeks after the risk contact, the test can miss an infection.
If you urinated less than 1 hour before collecting the sample, or catch more than the first part of the stream, the sample is diluted and the test can miss an infection.
Urine is slightly less sensitive than a urethral swab taken by a doctor.
Up to 3 to 4 weeks after treatment, the test can be positive due to leftover genetic material.

Preparation

Collect the urine when you have not passed urine for at least 1 hour.
Collect only the first part of the stream, not the middle part.

Who it is for

Who is the test useful for?

Useful for

In men, the result is most meaningful with urethral symptoms that have lasted longer than 4 weeks while chlamydia and gonorrhea have been ruled out, and if a sexual partner has trichomonas. For men without symptoms, the chance of a positive result is low.

How common is it?

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.

Multidisciplinary guideline on STIs (GP registration 2020); the LCI guideline on Trichomonas vaginalis (Sexual Health Centers 2022)

Drawbacks 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.

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