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Chlamydia IgG: what antibodies in your blood say about contact with chlamydia

After contact with a bacterium, your immune system makes IgG antibodies, proteins aimed at exactly that one germ, and according to MedlinePlus the body remembers them even after the infection has cleared. Chlamydia IgG are the IgG antibodies the body makes against chlamydia bacteria.

If there are chlamydia antibodies in your blood, that can fit an infection now, an infection that is already over or treated, or another chlamydia species, according to the RIVM. Only a blood test shows whether you have those antibodies.

Star-SHL calls its test 'Chlamydia species IgG' and gives 'negative' as the expected result, without a unit.

Doctor's Assessment Included

The chlamydia IgG test looks in the blood for antibodies against chlamydia, which the body makes after contact with the bacterium. Normally the result is negative.

  • A chlamydia antibody test cannot tell an earlier infection from one that is still active; for a current infection, a PCR test on urine or a swab is the usual test.
  • A negative chlamydia antibody test does not rule out an infection: not everyone makes measurable antibodies, and the test is less sensitive than a PCR test.
  • In a fertility work-up, a positive chlamydia antibody test (CAT) counts as a risk factor for damage to the fallopian tubes.

Reference Ranges

Expected result Negative

Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.

Check your own value

Chlamydia IgG: what this test measures

The chlamydia IgG test checks whether IgG antibodies against chlamydia are present in your serum and gives positive or negative as the result, without a unit.

Chlamydia IgG: why this value matters

Chlamydia antibodies can also come from a common airway bacterium, because antibodies against the different chlamydia species cross-react a great deal, according to the RIVM. According to the RIVM, more than 60% of people aged 20 to 30 have antibodies against the airway bacterium Chlamydia pneumoniae, and in older people it is 75 to 80%.

Chlamydia IgG: how the blood test works

Referral
No GP referral needed. After the order we arrange the referral through ZorgDomein, within one business day; orders after 17:00 or at the weekend start on the next business day. ZorgDomein emails a barcode, and that barcode is what the draw site needs.
The draw
A blood draw from a vein in the arm, at a partner laboratory's draw site. No home kit, no finger prick.
Where
650+ draw sites run by independent laboratories across the Netherlands. Draw sites

Chlamydia IgG: when is testing worthwhile?

According to the RIVM, a chlamydia antibody test cannot tell an infection now from a cleared or treated infection, and for an infection now a NAAT is the usual test: it detects genetic material of the bacterium in urine or a swab. According to the RIVM, a NAAT gives a reliable result two weeks after possible contact.

Chlamydia IgG: symptoms of a high or low value

Low Levels

A negative chlamydia IgG result is the expected result at Star-SHL, but the antibodies can fade again after an infection. In an English study of women attending sexual health clinics, one research test still found antibodies in 49.3% two or more years after a first chlamydia diagnosis.

High Levels

A positive chlamydia IgG result means that your blood contains antibodies against a chlamydia species, and according to the RIVM the blood test cannot say whether the infection is still active. Symptoms that can fit chlamydia according to the RIVM are burning urination, unusual discharge and, in women, bleeding between periods or pain in the lower abdomen.

Chlamydia IgG: causes of a low or high value

What raises the value

  • Earlier chlamydia infection

    Chlamydia antibodies can come from an infection that has already cleared or been treated.

  • Current, untreated infection

    A chlamydia infection that is still present can also give a positive result; the chlamydia blood test cannot tell a current infection from an earlier one.

  • Other chlamydia species

    Depending on the test, antibodies against other chlamydia species can cross-react, for example antibodies against the airway bacterium Chlamydia pneumoniae; the RIVM notes much cross-reaction between chlamydia species.

Chlamydia IgG: lifestyle and this value

A positive chlamydia IgG result with symptoms or a recent risk is one to discuss with your GP. Consistent condom use reduces the chance that chlamydia is passed on during sex, according to the RIVM, although according to the RIVM condoms are not always used in time or correctly.

Chlamydia IgG: frequently asked questions

Can a positive chlamydia IgG result come from an airway infection?

Yes, a positive chlamydia IgG result can come from an airway infection: antibodies against the different chlamydia species cross-react a great deal according to the RIVM, and according to the RIVM Chlamydia pneumoniae is a common cause of airway infections. A positive-or-negative result does not show which species caused the antibodies.

Do chlamydia antibodies always stay in your blood?

No, chlamydia antibodies do not stay measurable in everyone: in an English study of women attending sexual health clinics, the share with antibodies on one research test fell to 49.3% two or more years after a first diagnosis.

Which chlamydia IgG test does Star-SHL use?

Star-SHL calls its chlamydia antibody test in serum "Chlamydia species IgG", with negative as the expected result. The RIVM writes that there is a lot of cross-reaction between the different chlamydia species.

Chlamydia IgG: sources

  1. RIVM, LCI-richtlijn Chlamydia trachomatis en lymphogranuloma venereum, vastgesteld 25 juni 2024, geraadpleegd 2026-10-05 (retrieved 2026) lci.rivm.nl
  2. RIVM, LCI-richtlijn Chlamydia pneumoniae, hoofdstuk Diagnostiek vastgesteld 5 april 2019, geraadpleegd 2026-10-05 (retrieved 2026) lci.rivm.nl

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Chlamydia IgG

€49,-