Assay

Immunoglobulins

Key Words

IG, IgA, IgG, IgM

Specimen Collection

Serum (brown)

Turnaround Time

72hrs

Test Indications

This laboratory assays immunoglobulins as a panel of IgA, IgG and IgM for the investigation of immune deficiencies. Indications for the measurement of each Ig class are listed below.
IgA: The most common cause of IgA deficiency is selective IgA deficiency that occurs in 1/700 in the normal population. This most often causes no clinical phenotype. Deficient IgA with another Ig isotype, particularly IgG is likely to be indicative of genetic immune deficiency.
IgG: Polyclonal IgG increases may be present in systemic lupus erythematosis, chronic liver diseases (infectious hepatitis and Laennecs cirrhosis), infectious diseases and cystic fibrosis. A monoclonal form of IgG increases in IgG-myeloma. Decreased synthesis of IgG is found in congenital (e.g. Bruton type agammaglobulinemia, a B Cell Deficiency), acquired immunodeficiency diseases and selective IgG subclass deficiencies. Decreased IgG concentrations are seen in protein-losing enteropathies, nephrotic syndrome and through the skin from burns. Increased IgG metabolism is found in Wiskott-Aldrich syndrome, myotonic dystrophy and with anti-immunoglobulin antibodies. Reduced serum IgG concentrations may be seen in myeloma patients with a paraprotein clonality of IgA or IgM (Waldenstroms macroglobulinemia) (very rarely IgD or IgE) as the normal bone marrow is destroyed by the malignant neoplasm.
IgM: Increased polyclonal IgM levels are found in viral, bacterial, and parasitic infections, liver diseases, rheumatoid arthritis, scleroderma, cystic fibrosis and heroin addiction. Monoclonal IgM is increased in Waldenstrom's macroglobulinemia. Increased loss of IgM is found in protein-losing enteropathies and in burns. Decreased synthesis of IgM occurs in congenital and acquired immunodeficiency syndromes. Reduced serum IgM concentrations may be seen in myeloma patients with a paraprotein clonality of IgA or IgG (very rarely IgD or IgE) as the normal bone marrow is destroyed by the malignant neoplasm. Due to the slow onset of IgM synthesis, the IgM concentration in serum from infants is lower than in that from adults.

Limitations/Interferences

It is known that the paraproteins secreted in monoclonal gammopathies (monoclonal immunoglobulinemia) may differ from the respective immunoglobulins of polyclonal origin by amino acid composition and size. This may impair the binding to antibody and hence impair accurate quantitation of total Ig concentration for a class (IgX polyclonal + IgX monoclonal). Therefore, serum electrophoresis is undertaken in all patients >35 years old undergoing immunoglobulin investigations.

Reference Range

IgA: 0.8-2.8 g/L
IgG: 5.3-16.5 g/L
IgM: 0.5-1.9 g/L

Analytical Error

IgA: 1.8%
IgG: 1.2%
IgM: 1.4%

Reference Change Value

IgA: 15.8%
IgG: 12.9%
IgM: 16.8%

Minimum retesting interval

Requests made within 14 days of a previous result on a patient are intervened