How are proteins classified in serum protein electrophoresis (SPEP)?

Albumin

Albumin represents the highest peak in serum protein electrophoresis, usually seen as a single, tall band. Occasionally, however two equally staining bands, referred to as bisalbuminemia or a widely staining band may be seen, which both represent normal variations. ^[9] Common conditions associated with decreased albumin include malnutrition, cirrhosis and nephrotic syndrome. Dehydration, on the other hand, causes a high albumin.

An area between albumin and the alpha-1 band is called the albumin-alpha-1 interzone. Even staining in this zone is caused by alpha-1 lipoprotein (High-density lipoprotein or HDL). An increase is usually seen in alcoholic liver disease, pregnancy and during puberty. A sharp band may also be seen in those with hepatocellular carcinoma as a result of elevated alpha-fetoprotein (AFP). ^[1]

Alpha zone

The alpha-1 fraction includes alpha-1 antitrypsin, transcortin, and thyroid-binding globulin. ^[9] Alpha-2 fraction is comprised of ceruloplasmin, alpha-2 macroglobulin, and haptoglobin. Both alpha-1 and 2 represent the acute phase reactants; hence, malignancy, infection or any inflammatory condition can cause their elevation. A relative increase in alpha-2 fraction may be seen in nephrotic syndrome due to the relative larger size of the proteins and the inability to pass through the glomeruli. A decrease in alpha-1 component may be seen in alpha-1 antitrypsin deficiency and a decrease in alpha-2 component may be seen in hemolytic anemia due to decreased haptoglobin levels.

Beta zone

The beta zone consist of beta-1 and beta-2 but is often represented a graphically as a single band. Beta-1 consists mostly of transferrin, and is increased in conditions such as iron-deficiency anemia, pregnancy and estrogen therapy. B-lipoprotein and C3 complement are included in the B-2 component. ^[5] IgA, IgM, and sometimes IgG can occasionally be identified in the beta fraction as well.

Gamma zone

Immunoglobulins mainly comprise this area including IgG, IgA, IgM, IgD and IgE. Agammaglobulinemia and hypogammaglobulinemia syndromes such as IgA deficiency are associated with a decrease in this area. Various inflammatory, autoimmune and hematologic, and non-hematologic diseases are associated with an increased gamma peak. However, a homogenous, spike-like increase in the gamma region is of special interest as it may represent an abnormal expansion of immunoglobulin-producing plasma cells.