STIs
Chlamydia trachomatis PCR (swab)
PCR test for genetic material of the chlamydia bacterium in a self-collected swab from the vagina, anus or throat.
What it measures
Chlamydia is an STI caused by the bacterium Chlamydia trachomatis. The PCR looks for genetic material of the bacterium in material that you collect yourself with a cotton swab from the vagina, the anus or the throat. According to the LCI guideline (RIVM), a self-collected vaginal swab in women is more sensitive than urine. The result only applies to the place where the swab was taken; an infection in another place is not found this way.
- A current chlamydia infection of the vagina and cervix, even if it causes no symptoms
- A chlamydia infection of the anus, which usually causes no symptoms
- A chlamydia infection of the throat, which rarely causes symptoms and often no longer comes from living bacteria
Positive
A positive result means that genetic material of the chlamydia bacterium was found. This usually fits a current infection, even if you have no symptoms: up to 9 in 10 women and about half of men notice nothing. Chlamydia can be treated well with antibiotics. Without treatment, the infection often clears up on its own over time, but in women it can sometimes spread upward and cause inflammation of the womb and fallopian tubes; according to the LCI guideline (RIVM), the chance of permanent infertility after chlamydia is small (0.5 to 1 percent). According to the guidelines, a positive throat result usually has no consequences for treatment, because chlamydia in the throat rarely causes symptoms and the material found often does not come from living bacteria.
Negative
A negative result means that no chlamydia was found at the sampled site. According to the LCI guideline (RIVM), the test is reliable from 2 weeks after the last risky sexual contact; within those 2 weeks, an infection can still be missed. A negative vaginal swab does not rule out chlamydia in the anus, and vice versa. If your symptoms continue, there may be another cause.
If your result is abnormal
With a positive result, the GP usually prescribes a course of antibiotics and advises no sex for a week; the GP discusses warning sexual partners and testing for other STIs such as gonorrhea, HIV and syphilis. For men who have sex with men with chlamydia in the anus, the LCI guideline (RIVM) advises additional testing for LGV, a form of chlamydia that can be more severe. Individual cases of chlamydia are not notifiable.
Reliability
According to the LCI guideline (RIVM) and the Multidisciplinary Guideline on STIs, the PCR (a NAAT: a test that multiplies genetic material of the bacterium and so detects it) is the standard test for chlamydia, with high sensitivity and specificity on urine and self-collected swabs. For men, first-void urine is the usual sample; in women, a vaginal swab is more sensitive than urine. According to the LCI guideline, a negative result is reliable from 2 weeks after the risky sexual contact. Because the test detects genetic material, it can still be positive for up to a few weeks after treatment.
Limitations
- Less than 2 weeks after the risky sexual 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 falsely negative result.
- Chlamydia in the throat is rare, almost never causes symptoms and is often no longer a living bacterium; a positive throat result therefore says little about an infection that needs treatment.
- Within 3 weeks after treatment, the test can be positive due to leftover genetic material, even if the infection is gone.
How common is this
Chlamydia is the most common bacterial STI in the Netherlands. In 2024, the sexual health centers of the GGD (municipal public health service) found chlamydia in 20,174 people, two thirds of whom had no symptoms; GPs made the diagnosis about 43,000 times in 2023. Chlamydia is most common in young people under 25.
Who is this useful for
A vaginal swab is useful for women (and other people with a vagina) with symptoms that may fit chlamydia, such as changed discharge, bleeding between periods or after sex, or pain when urinating, and for anyone whose sexual partner has chlamydia. An anal swab is useful with symptoms at the anus, after anal sex and for men who have sex with men. Without symptoms, the benefit of a positive result is uncertain, because many infections clear up on their own. A throat swab says little, because chlamydia in the throat rarely causes symptoms and a positive throat result usually has no consequences.
Downsides and risks
- A positive result without symptoms usually leads to antibiotic treatment of an infection that might have cleared up on its own; unnecessary antibiotic use contributes to resistance.
- A positive throat result can cause worry and treatment without any proven benefit for your health.
Sources
- RIVM-LCI-richtlijn Chlamydia trachomatis en lymphogranuloma venereum (2024, diagnostiek en meldingsplicht)
- RIVM: Leidraad en stroomschema Testen op chlamydia (januari 2025)
- Multidisciplinaire Richtlijn Seksueel overdraagbare aandoeningen (2024), module C1 Chlamydiasis
- Thuisarts.nl: Ik heb chlamydia
- RIVM: Chlamydia (cijfers 2024)
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