Rubella Igg & Reflex Avidity

Rubella IgG & Reflex Avidity

What it is

The Rubella IgG & Reflex Avidity test measures IgG antibodies against the rubella virus and, when positive, assesses the strength (avidity) of these antibodies. Rubella IgG indicates past infection or vaccination, while avidity testing helps differentiate between a recent infection and one that occurred months or years earlier. This distinction is particularly important in pregnancy, where recent infection can lead to congenital rubella syndrome (CRS) in the fetus.

Uses

This test is used to:

• Determine immunity to rubella due to past infection or vaccination.
• Differentiate recent primary infection from past infection in Rubella IgG positive cases.
• Evaluate rubella exposure during pregnancy and assess risk to the fetus.
• Guide clinical decision-making for suspected rubella infections in pregnant women.
• Support public health monitoring during rubella outbreaks.

Symptoms / Conditions That May Lead to the Test

Doctors may recommend this test if you have:

• Uncertain or undocumented rubella vaccination history.
• Pregnancy and need immunity confirmation.
• Possible exposure to rubella during pregnancy.
• Rash, fever, swollen lymph nodes, or joint pain suggesting rubella.
• Participation in routine prenatal or fertility workups.

Abnormal Results

• Positive IgG with High Avidity: Indicates past infection or vaccination. High avidity antibodies usually develop >3 months after exposure, suggesting immunity and minimal risk in pregnancy.
• Positive IgG with Low Avidity: Suggests a recent rubella infection (within the past 2–3 months). This is clinically significant in pregnant women due to risk of congenital rubella syndrome.
• Negative IgG: Indicates no immunity, meaning susceptibility to rubella. Vaccination is recommended for non-pregnant women of childbearing age.

Risks

The test requires a routine blood sample. Risks are minimal and may include:

• Mild pain or discomfort at the needle site.
• Minor bruising or bleeding.
• Rare dizziness or fainting after blood draw.