Serum or plasma mass concentration of immunoglobulin G (IgG) subclasses (specifically IgG1, IgG2, IgG3, IgG4) using immunoassay or related method

Why This Test Is Done

Doctors may order IgG subclass testing if you have symptoms of a weakened immune system, such as frequent infections, unusual bruising, or unexplained bleeding. It may also be used to monitor conditions like certain autoimmune diseases, immune deficiencies, or after treatments that affect the immune system.

What to Expect Before the Test

Blood is collected in a tube and sent to a lab for analysis. The lab will separate the serum or plasma from the blood cells and measure the concentration of each IgG subclass using a sensitive immunoassay method.

What the Results Mean

IgG subclasses are measured in grams per deciliter (g/dL) or milligrams per deciliter (mg/dL). Your results will be compared to standard reference ranges provided by the lab. Low levels of certain IgG subclasses may suggest immune system issues, while high levels might indicate conditions like chronic infections or certain autoimmune disorders.

Possible Conditions or Concerns

Low IgG levels, particularly in specific subclasses, may be linked to conditions like Common Variable Immunodeficiency (CVID), HIV/AIDS, or other immune deficiencies. High IgG levels can sometimes be seen in chronic infections, certain cancers, or autoimmune diseases like rheumatoid arthritis.