Quantitative serum immunoglobulin tests.

What is the test? Immunoglobulins are protein molecules. They contain antibody activity and are produced by the terminal cells of B-cell differentiation known as 'plasma cells'. There are five classes of immunoglobulin (Ig): IgG, IgM, IgA, IgD and IgE. In normal serum, about 80% is IgG, 15% is IgA, 5% is IgM, 0.2% is IgD and a trace is IgE. Quantitative serum immunoglobulin tests are used to detect abnormal levels of the three major classes (IgG, IgA and IgM). Testing is used to help diagnose various conditions and diseases that affect the levels of one or more of these immunoglobulin classes. Some conditions cause excess levels, some cause deficiencies, and others cause a combination of increased and decreased levels. IgD and IgE will not be discussed in this article.