24-72 hours after setup at PeaceHealth Laboratories’ reference lab
Specimen Collection Details
One 7.5 mL serum separator tube (SST). Also acceptable: One 4 mL green top tube (heparin).
Allow to clot, centrifuge and separate serum or plasma from cells and immediately pour into a plastic vial.
2 hours ambient, 8 days refrigerated, or 6 months frozen.
2 mL serum or plasma.
0.45 mL serum or plasma.
The total IgG (mg/dL) can be derived from the sum of the subclass IgG1, IgG2, IgG3, and IgG4 values. However, a confirmatory and more precise total IgG is available by the nephelometric method of quantitation for total IgG. Refer to Immunoglobulin G (IgG) (44400).
IgG Subclass 1
IgG Subclass 2
IgG Subclass 3
IgG Subclass 4
The IgG class of immunoglobulin is composed of four subclasses designated IgG1, IgG2, IgG3, and IgG4. Each subclass has a slightly different gamma-heavy chain, but all IgG molecules are recognized by class-specific anti-IgG antisera. The subclasses as measured in serum occur in the relative proportion of 16:6:2:1. Antipolysaccharide antibodies are preferentially IgG2; antibodies that recognize protein antigens are preferentially IgG1 and IgG3. In spite of normal IgG levels, a selective loss of an IgG subclass may result in a humoral immune deficiency. Diminished levels of all IgG subclasses are found in several primary immunodeficiency diseases, including common variable hypogammaglobulinemia, ataxia telangiectasia, and Wiskott-Aldrich syndrome. Isolated IgA deficiency is relatively common and is often asymptomatic; however, among IgA-deficient individuals with recurrent sinopulmonary infuctions, there is a high frequency of concurrent IgG2 and/or IgG4 deficiency. Selective deficiencies of IgG subclasses have been found in children with recurrent sinopulmonary infections and otitis media. Both isolated and combined deficiencies of IgG2, IgG3, and IgG4 have been reported. In these children, specific antibody responses to Haemophilus influenzae type B and/or Streptococcus pneumoniae are deficient in spite of normal total IgG levels. This test is useful for investigating recurrent respiratory infections, recurrent otitis media, and impaired lung function with or without IgA deficiency.