Toxoplasma IgG

Key Aspects of Toxoplasma IgG Testing

• Purpose: Measures IgG antibodies indicating past infection and potential immunity. It is critical for pregnant women, often part of the TORCH panel to screen for congenital transmission.
• Interpretation:
  • Negative IgG / Negative IgM: No prior exposure, susceptible to infection.
  • Positive IgG / Negative IgM: Past infection, immunity present.
  • Positive IgG / Positive IgM: Potential recent infection or reactivation; further testing (like IgG avidity) might be required.
• Result Timing: IgG levels usually rise 7–14 days after infection, often replacing IgM as the long-lasting antibody.
• Procedure: A blood sample is taken, usually from the arm, with no fasting required.
• Accuracy: Highly accurate but depends on the timing of the test.

What Positive IgG Means

A positive result typically means you have previously been exposed to the parasite. In most healthy individuals, this confirms immunity and that a new infection did not occur during pregnancy.

Why IgG Avidity Tests are Used

If both IgG and IgM are positive, doctors may order a Toxoplasma IgG avidity test to determine how long ago the infection occurred. A "high avidity" result can rule out a recent infection within the past 4 months.