Serum Immunoglobulin G (IgG) Subclass Measurement (Quantitative)

What Does This Test Measure?

IgG is the most abundant antibody in your blood, but it is divided into four subclasses (IgG1, IgG2, IgG3, IgG4). This test typically assesses one or more of these subclasses to evaluate immune response, antibody production, or potential deficiencies. Some tests may focus on total IgG while others break it down by subclass.

Why Might You Need This Test?

Doctors may order IgG subclass testing if you have recurrent infections, autoimmune conditions, immune system disorders (like common variable immunodeficiency), or if certain medications (e.g., steroids) are affecting your antibody levels. It can also help monitor treatment progress in conditions like HIV or certain cancers.

What Does It Mean If Results Are Abnormal?

Low levels of specific IgG subclasses may indicate weakened immune function, while elevated levels could suggest chronic inflammation, autoimmune diseases, or certain infections. Your doctor will interpret results in the context of your symptoms and medical history.

How Is This Test Performed?

A blood sample is drawn from a vein, usually in your arm. The serum is then separated and analyzed using immunoassay methods (such as nephelometry or electrochemiluminescence) to measure antibody concentrations.