Immunoglobulin G (IgG) Subclass 1, 2, 3, and 4 Quantification (Serum)

What Does This Test Measure?

IgG is divided into four subclasses (IgG1, IgG2, IgG3, and IgG4), each with different roles in immunity. This test quantifies each subclass separately, allowing for detailed assessment of immune function. IgG1 and IgG2 are most involved in fighting bacterial infections, while IgG3 is highly active in immune responses and IgG4 is less common but may play a role in allergic reactions or chronic inflammation.

Why Might You Need This Test?

Doctors may order this test if you have symptoms like frequent infections, autoimmune conditions, or immune system disorders. It can also be used to monitor treatment responses in conditions like lupus, rheumatoid arthritis, or certain immunodeficiency diseases.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The blood is processed to separate the serum (liquid part without clots) for testing. This test requires a fresh serum sample and should be analyzed promptly to ensure accurate results.

What to Expect Before the Test

No special preparation is needed for this test. However, inform your healthcare provider about any medications you’re taking, especially steroids or immune-modifying drugs, as they can affect IgG levels.