Immunoglobulin G (IgG) Subclass Quantification (Serum/Plasma)

Why This Test Is Done

Your healthcare provider may order this test if you have symptoms like frequent infections, autoimmune conditions, or if you’re being evaluated for immune-related problems. It can also help diagnose or monitor conditions affecting your immune system, such as certain infections, allergies, or immune deficiencies.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if your blood is drawn early in the morning. Bring any medications or supplements you’re taking to your appointment.

A healthcare professional will draw blood from a vein in your arm using a small needle. You may feel a brief sting, but it usually doesn’t cause much discomfort. The blood sample will be sent to a lab for analysis.

The blood sample is tested using an immunoassay method to measure the specific IgG subclasses (IgG1, IgG2, IgG3, IgG4) in your serum or plasma. Results help determine if your immune response is functioning normally or if there are imbalances.

What the Results Mean

Results show the concentration of each IgG subclass. While reference ranges vary by lab, lower or higher-than-expected levels may suggest conditions like hypogammaglobulinemia (low IgG) or certain autoimmune diseases (e.g., elevated IgG4). Your provider will interpret the results in the context of your health history and symptoms.