Toxoplasmosis IgG Avidity
The Toxoplasmosis IgG Avidity Test measures the strength with which IgG antibodies bind to the Toxoplasma gondii parasite.
After infection, IgM antibodies are produced first, followed by IgG antibodies. In the first few months after infection, these IgG antibodies still bind relatively weakly (low avidity). As time passes, the antibodies become stronger and their avidity increases.
As a result, the test can help distinguish between:
- a recent infection (low avidity);
- an infection that occurred some time ago (high avidity).
When is this test useful?
The Toxoplasmosis Avidity Test is usually ordered when:
- if a toxoplasmosis IgM test is positive;
- both IgG and IgM are positive;
- It is unclear when the infection occurred;
- During pregnancy, it is important to determine whether an infection has occurred recently.
Why is this important?
In healthy people, a toxoplasmosis infection usually causes no symptoms or only mild ones. However, during pregnancy, a recent infection can pose risks to the unborn child. The avidity test therefore helps to better determine whether the infection occurred before or during pregnancy.
How should the results be interpreted?
- Low avidity: may indicate a recent infection (usually within the past few months).
- High avidity: makes a recent infection highly unlikely and usually indicates an infection that occurred some time ago.
- Intermediate avidity: The result is inconclusive and must always be evaluated in conjunction with the IgG and IgM results and the clinical presentation.
Please note: The avidity test is not a standalone diagnostic test. The results must always be interpreted in conjunction with the Toxoplasmosis IgG and IgM tests and, if necessary, by a doctor.
For more information, see: http://www.rivm.nl/Onderwerpen/T/Toxoplasmose/Toxoplasmose_en_zwangerschap
