CMV IGG & REFLEX AVIDITY

CMV IgG & Reflex Avidity

What it is

The CMV IgG & Reflex Avidity test measures the presence of IgG antibodies against cytomegalovirus (CMV) and evaluates their avidity (binding strength). CMV is a common herpesvirus that can cause complications in pregnancy and immunocompromised individuals. The IgG test shows prior exposure, while the avidity test helps determine whether the infection is recent or past.

Uses

This test is mainly used in pregnant women and immunocompromised patients to assess CMV infection timing. IgG positivity indicates prior infection or immunity. Reflex avidity testing helps differentiate primary (recent) infection from past infection, which is crucial during pregnancy because primary CMV infection carries the highest risk of congenital transmission to the fetus.

Symptoms That May Lead to the Test

Doctors may order this test if you have symptoms of CMV such as fever, fatigue, swollen glands, muscle aches, or unexplained hepatitis-like illness. In pregnancy, it may be requested after abnormal ultrasound findings (growth restriction, calcifications, microcephaly, hydrops fetalis) that suggest congenital infection.

Abnormal Results

Positive CMV IgG with Low Avidity: Suggests a recent primary CMV infection (within the past 3–4 months), particularly important in pregnancy.

Positive CMV IgG with High Avidity: Indicates a past infection, generally reducing the risk of congenital CMV transmission.

Negative CMV IgG: Indicates no prior exposure. These patients are susceptible to primary infection and require preventive measures during pregnancy or before immunosuppressive therapy.

Risks

The test involves a standard blood draw with minimal risks, such as mild pain, slight bruising, or dizziness at the puncture site. The laboratory reflex testing (avidity) carries no additional risk to the patient but provides critical diagnostic insight.