Immunoglobulin G (IgG) Subclass 1 and 2 with Serum Immunoglobulin Total and Antibody Index (Serum)

Why This Test Is Done

Your healthcare provider may order this test if you have symptoms of a weakened immune system, such as frequent infections, unexplained fatigue, or if you’re being evaluated for conditions like immunodeficiency, autoimmune diseases, or after receiving certain treatments (e.g., chemotherapy or monoclonal antibody therapy). It may also be used to monitor immune response to vaccines or diseases like HIV.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into a vein (usually in your arm) to draw blood. The process takes about 5 minutes. If you’re nervous, let your provider know—they can offer options like a numbing cream or a different vein to make it more comfortable.

What the Test Results Mean

Results show your total IgG level and breakdown of IgG1 and IgG2 subclasses, as well as an antibody index. Lower-than-expected IgG levels or imbalances between subclasses may indicate immune dysfunction. Higher-than-expected levels could suggest conditions like multiple myeloma or chronic infections.

Common Conditions Linked to IgG Testing

IgG subclass testing helps diagnose or monitor conditions like primary immunodeficiency (e.g., common variable immunodeficiency), autoimmune diseases (e.g., rheumatoid arthritis), or evaluate immune responses in patients with chronic illnesses or undergoing treatments that suppress immunity.