Immunoglobulin G (IgG) Subclass Measurement (Serum)

What Does This Test Measure?

IgG is divided into four subclasses (IgG1, IgG2, IgG3, IgG4), each with distinct roles. This test evaluates the concentration of these subclasses in your blood serum. Variations can indicate immune system health, response to vaccines, or underlying conditions like autoimmune diseases.

Why Might You Need This Test?

Doctors may order this test if you have symptoms of immune system issues (e.g., frequent infections, fatigue), suspected immunodeficiency, or if you’ve had a recent vaccine to check your immune response. It can also help diagnose conditions like lupus, rheumatoid arthritis, or certain infections.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The blood is processed to separate serum (the liquid part after clotting), which is then analyzed for IgG subclass levels. No special preparation is needed, but fasting may be advised depending on the clinical context.

Common Reasons for Abnormal Results

Low levels of certain IgG subclasses may suggest immune deficiencies, poor vaccine responses, or chronic illnesses. High levels could indicate overactive immune responses, infections, or certain autoimmune conditions. Results are interpreted in the context of your overall health and symptoms.