Serum / urine protein electrophoresis, Immunofixation/Immunotyping,

Monoclonal proteins (paraproteins) comprise whole immunoglobulin and/or free light chains. Single or multiple monoclonal proteins may be present in patients with multiple myeloma, B-lymphoproliferative disorders and amyloidosis. Small paraproteins may occur after an infection when they are transient and in the older age individual, monoclonal gammopathy of undetermined significance (MGUS). The initial test to detect and identify the paraprotein is serum protein electrophoresis. When a monoclonal band is found on serum protein electrophoresis which is done by a capillary tube method in this laboratory, further tests are initiated to type the immunoglobulin class and light chain. This is done by serum immunofixation or immunotyping.

Serum capillary electrophoresis may not detect all paraproteins due to factors like low concentration, inadequate electrophoretic separation or being present only in urine. In such instances quantifying serum free kappa and lambda light chains, calculating the κ:λ ratio and urine protein electrophoresis may help identify monoclonal proteins. The κ:λ ratio may be abnormal in amyloidosis, light chain disease and in impaired renal function.