Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1217 page)

   Physiologic (newborn)

   Immunodeficiencies, induced (steroids, immunosuppressants, chemotherapy, radiotherapy)

   Suppressed synthesis caused by monoclonal gammopathies (multiple myeloma, light chain disease, amyloidosis)

   Lymphomas, leukemias

   Limitations

   The presence of a circulating monoclonal protein may interfere with one of more laboratory tests performed on liquid-based automated analyzers, either by precipitating during the analysis or by virtue of its specific binding properties.

   A small M-protein may be present even when quantitative immunoglobulin values, beta and gamma mobility components on SPEP, and total serum protein concentrations are all within normal limits.

   Fibrinogen (in plasma) is seen as a discrete band between the beta and gamma mobility regions. This is indistinguishable from an M-protein; the addition of thrombin to the specimen produces a clot if fibrinogen is present. The presence of fibrinogen is established if the discrete band is no longer detected when electrophoresis is repeated after the addition of thrombin.

   Hb-Hp complexes secondary to hemolysis may appear as a large band in the alpha-2 globulin region.

   High concentrations of transferrin in patients with iron deficiency anemia may produce a localized band in the beta region.

   Nephrotic syndrome is often associated with increased alpha-2 and beta bands, which can be mistaken for an M-protein. Serum albumin and gammaglobulin concentrations are usually reduced in this setting.

   Nonspecific increases in acute-phase reactants or certain hyperlipoproteinemias may result in increases in alpha-1 bands.

   Serum IF is more sensitive than SPE and also determines the heavy and light chain type of the monoclonal protein. However, unlike SPE, IF does not give an estimate of the size of the M-protein (i.e., its serum concentration) and thus should be done in conjunction with electrophoresis.