Serum protein electrophoresis and immunofixation electrophoresis are critical laboratory assays in the identification of monoclonal proteins.  Monoclonal proteins, also called “M spikes” or “paraproteins,” may be due to monoclonal gammopathy of undetermined significance, but they may also indicate malignant diagnoses such as multiple myeloma or lymphoplasmacytic lymphoma.

Protein electrophoresis separates the proteins in a patient sample by their size and charge and allows for the detection of abnormal monoclonal proteins.  Immunofixation electrophoresis is used to determine the type of monoclonal protein present.  Both methods are technically challenging and require interpretation by a qualified laboratory professional.

Occasionally, anomaly such as immunoglobulin complexes or temperature sensitive cryoglobulins distort the protein separation and prevent accurate interpretation of test results.

A case study published in the July 2019 issue of the Journal of Applied Laboratory Medicine describes a patient whose monoclonal protein was not identifiable by routine protein electrophoresis and immunofixation methods.  The Case Report suggests steps that laboratories may take to reduce artifacts and identify monoclonal proteins accurately.