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Immunoglobulin G

Test ID:

705148

CPT code:

82784

Synonyms:

Immunoglobulin G, Quantitative

IgG, Serum

Quantitative IgG, Serum

Clinical Use:

Evaluate humoral immunity; monitor therapy in IgG myeloma; evaluate patients, especially children and those with lymphoma, with propensity to infections

Test Information:

Immunoglobulin G is the major antibody containing protein fraction of blood. With significant decreases in IgG level, on either a congenital or acquired basis, there is an increased susceptibility to infectious processes ordinarily dealt with by humoral antibody (ie, bacterial infection). Thus, patients with repeated infection should have their immunoglobulins, and specifically IgG, measured. Therapy with exogenous γ-globulins may be efficacious in such patients. Conversely, IgG levels will be increased in immunocompetent individuals responding to a wide variety of infections or inflammatory insults (indeed, this represents the basis of the serologic diagnosis of infectious diseases). IgG specific antibody can now be demonstrated for numerous organisms, and when coupled with IgM specific antibody, can give an accurate diagnosis of acute or chronic infection. Today, a major cause for a polyclonal increase in IgG is the acquired immunodeficiency syndrome. Monoclonal IgG can be demonstrated in many cases of multiple myeloma. 3 g/dL of monoclonal IgG is a major diagnostic criterion for myeloma. Oligoclonal IgG can be seen in multiple sclerosis and some chronic hepatitides.
A monoclonal gammopathy may be present when the total IgG value is in the normal range. While many of these patients do not have multiple myeloma, evaluation of these patients for evaluation of the gammopathy and the presence of Bence Jones protein in urine is important.

Specimen Type:

Serum

Requested Volume:

1 mL (adult), 0.4 mL (pediatric)

Container Type:

Red-top tube or gel-barrier tube

Storage Instructions:

Samples suspected of having macroglobulins or cryoglobulins should be drawn and held at 37°C. Samples suspected of containing cold agglutinins should not be refrigerated prior to serum separation from clot.