Serum Immunofixation Electrophoresis and Quantitative Immunoglobulins in Plasma Cell Disorders

Introduction to SIFE and Quantitative Immunoglobulins

Serum Immunofixation Electrophoresis (SIFE) identifies and characterizes the specific type of monoclonal protein present, while quantitative immunoglobulins measure the total concentration of each immunoglobulin class in the blood, including both normal polyclonal and abnormal monoclonal proteins 1

The National Comprehensive Cancer Network recommends both SIFE and quantitative immunoglobulin tests as part of the initial diagnostic workup for suspected plasma cell disorders, as they provide different but complementary information 2, 3, 1
SIFE is essential for phenotyping monoclonal gammopathies and is considered the reference method for confirmation when an abnormal pattern is detected on serum protein electrophoresis, although the exact sensitivity is not provided in the relevant citation 1

SIFE answers "what type" of monoclonal protein is present, which is critical for diagnosis and classification 1
Quantitative immunoglobulins answer "how much" of each immunoglobulin class is present and can reveal immune paresis (suppression of normal immunoglobulins) 1

Quantitative immunoglobulins are superior for detecting suppression of uninvolved immunoglobulin classes, which is an important prognostic feature in multiple myeloma 1

Both tests are used for surveillance, with quantitative immunoglobulins plus quantitation of M-protein recommended at least every 3 months in patients with active myeloma 3
SIFE is repeated as clinically indicated to confirm the persistence or disappearance of the monoclonal protein during treatment 3