Toxoplasmosis IgG avidity (Toxoplasma gondii IgG avidity)
Determines IgG avidity to Toxoplasma gondii — indicator of 'antibody-antigen binding strength'. This test determines the timing of infection: recent (within the past weeks or months) or long ago (usually more than 3-4 months).
Especially important during pregnancy since: primary infection during pregnancy may be dangerous for the fetus; past infection usually indicates immunity presence. Therefore avidity is one of the most informative tests when infection timing needs to be determined.
Most commonly ordered when:
- IgM is positive or equivocal;
- IgG is positive and infection timing needs clarification;
- during pregnancy/pregnancy planning.
Infection routes:
- insufficiently cooked meat;
- unwashed vegetables/fruits/berries;
- contact with cat litter/soil;
- gardening without gloves.
Recommended for:
- pregnant women with IgM(+) or equivocal results;
- women planning pregnancy; i
- mmunocompromised patients (by physician prescription).
Biomaterial: Venous blood
- Draw blood fasting (8-12 hours without food)
- Water is permitted
- Exclude fatty food and alcohol 24 hours before
- No smoking 30 minutes before
Medications:
- If taking antiparasitic drugs, hormonal drugs, or immunosuppressants — inform physician;
- dose adjustment is usually not required unless directed by physician
- Pregnancy (TORCH screening with equivocal results);
- pregnancy planning;
- positive or equivocal IgM;
- need to clarify infection timing.
Note: Avidity is always evaluated together with IgG and IgM, and gestational age.
Low IgG avidity — probable recent infection (fresh infection).
High IgG avidity — infection was long ago, usually before pregnancy.
At low avidity or any equivocal results: infectious disease specialist and gynecologist consultation mandatory. Self-treatment not permitted.
