Immunoglobulin G (IgG), Serum
Detecting or monitoring of monoclonal gammopathies and immune deficiencies
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
The gamma globulin band as seen in conventional serum protein electrophoresis consists of 5 immunoglobulins. In normal serum, about 80% is immunoglobulin G (IgG).
Elevations of IgG may be due to polyclonal immunoglobulin production. Monoclonal elevation of IgG characterize multiple myeloma.
Monoclonal gammopathies of all types may lead to a spike in the gamma globulin zone seen on serum protein electrophoresis.
Decreased immunoglobulin levels are found in patients with congenital deficiencies.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
0-<5 months: 100-334 mg/dL
5-<9 months: 164-588 mg/dL
9-<15 months: 246-904 mg/dL
15-<24 months: 313-1,170 mg/dL
2-<4 years: 295-1,156 mg/dL
4-<7 years: 386-1,470 mg/dL
7-<10 years: 462-1,682 mg/dL
10-<13 years: 503-1,719 mg/dL
13-<16 years: 509-1,580 mg/dL
16-<18 years: 487-1,327 mg/dL
> or =18 years: 767-1,590 mg/dL
Increased serum immunoglobulin concentrations occur due to polyclonal or oligoclonal immunoglobulin proliferation in hepatic disease (hepatitis, liver cirrhosis), connective tissue diseases, acute and chronic infections, as well as in the cord blood of neonates with intrauterine and perinatal infections.
Elevation of immunoglobulin G may occur in monoclonal gammopathies such as multiple myeloma, primary systemic amyloidosis, monoclonal gammopathy of undetermined significance, and related disorders.
Decreased levels are found in patients with primary or secondary immune deficiencies.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Electrophoresis is usually required to interpret an elevated immunoglobulin class as polyclonal versus monoclonal. Immunofixation is usually required to characterize a monoclonal protein.
If there is a discrete M-peak, the monoclonal protein can be monitored with quantitative immunoglobulins. If immunoglobulin quantitation is used to monitor the size of a monoclonal protein which is contained in a back-ground of polyclonal immunoglobulins, however, changes in the immunoglobulin quantitation may reflect changes in the background immunoglobulins, and serum protein electrophoresis should therefore be used to monitor the monoclonal protein.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Webster ADB: Laboratory investigation of primary deficiency of the lymphoid system. In Clinics in Immunology and Allergy. Vol. 5. 3rd edition. Philadelphia, 1985, pp 447-468
2. Pinching AJ: Laboratory investigation of secondary immunodeficiency. In Clinics in Immunology and Allergy. Vol. 5. 3rd edition. Philadelphia, WB Saunders Company, 1985, pp 469-490
3. Dispenzieri A, Gertz MA, Kyle RA: Distribution of diseases associated with moderate polyclonal gammopathy in patients seen at Mayo Clinic during 1991. Blood 1997;90:353
4. Kyle RA, Greipp PR: The laboratory investigation of monoclonal gammopathies. Mayo Clin Proc 1978;53:719-739
5. Ballow M, O'Neil KM: Approach to the patient with recurrent infections. In Allergy: Principles and Practice. Vol. 2. 4th edition. Edited by E Middleton Jr, CE Reed, EF Ellis, et al. St. Louis, MO, Mosby-Year Book, Inc., 1993, pp 1027-1058
6. Kyle RA: Detection of quantitation of monoclonal proteins. Clin Immunol Newsletter 1990;10:84-86