Serum Immunoglobulins (IgG, IgA, IgM)
IgG, IgA, and IgM are the three quantitatively major antibody classes in blood. Together they protect against infection and defend mucosal surfaces (IgA). Quantitative immunoglobulin testing screens for immune deficiency (low levels, often with recurrent infections), polyclonal elevation (chronic infection, autoimmune disease, liver disease), and monoclonal gammopathy (multiple myeloma, Waldenström's, MGUS). Abnormal results often lead to protein electrophoresis and immunofixation.
Reference Ranges
Male
700 – 1600
mg/dL
Female
700 – 1600
mg/dL
Child
400 – 1600
mg/dL
Age-dependent; lower in first years of life
Reference ranges may vary by laboratory. Always compare with the range printed on your lab report.
What Low Levels Mean
Low immunoglobulins (especially IgG below 500 mg/dL) with recurrent sinopulmonary infections suggest common variable immunodeficiency (CVID), X-linked agammaglobulinemia in boys, selective IgA deficiency (the most common primary immunodeficiency), or secondary hypogammaglobulinemia from chronic steroid use, myeloma, nephrotic syndrome, or lymphoma. Immunology referral and IgG replacement therapy are sometimes needed.
What High Levels Mean
Polyclonal elevation (all immunoglobulins raised) is typical of chronic infection (HIV, chronic hepatitis), chronic inflammation, and autoimmune disease. Monoclonal elevation — a sharp 'M-spike' on protein electrophoresis with elevation of one class only — suggests monoclonal gammopathy, which may be benign (MGUS) or malignant (multiple myeloma, Waldenström's, lymphoma). The distinction is made with immunofixation, serum free light chains, bone marrow biopsy, and imaging.
Frequently Asked Questions
What is selective IgA deficiency?
The most common primary immunodeficiency — affects about 1 in 500 people. Most are asymptomatic, but some have recurrent sinopulmonary infections, atopy, or autoimmune disease. Importantly, IgA-deficient patients can have anti-IgA antibodies that cause anaphylactic reactions to blood products containing IgA — this should be noted on medical records and factored into transfusion planning.
What is MGUS and how is it followed?
Monoclonal gammopathy of undetermined significance — a small monoclonal immunoglobulin without myeloma, lymphoma, or organ damage. Present in ~3% of adults over 50 and 5% over 70. It progresses to myeloma, lymphoma, or related conditions at about 1% per year. Monitoring is with periodic electrophoresis, light chains, calcium, creatinine, and CBC — typically every 6–12 months.
When should immunoglobulins be tested?
Recurrent sinopulmonary infections (more than 4 per year, especially bacterial), atypical infections or unusual organisms, chronic diarrhea suggesting mucosal immune failure, unexplained anemia or bone pain in older adults (myeloma screening), and workup of autoimmune disease. The panel is also used preoperatively in patients at high risk of complicated infection.
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This information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
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