Monoclonal Gammopathy of Undetermined Significance (MGUS)
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The following questions were submitted by viewers and answered by the presenter, Jerry Katzmann, PhD, from the Division of Clinical Biochemistry and Immunology at Mayo Clinic in Rochester, Minnesota. Questions are presented as submitted (unedited).
Free light chain analysis—should this be offered as a panel?
The assays for quantitative free light chain (kappa and lambda free light chain) are offered as a single test (#84190, Immunoglobulin Free Light Chains, Serum) as well as in a panel of serum protein electrophoresis, immunofixation electrophoresis, and free light chain (#87997, Monoclonal Protein Study, Expanded Panel, Serum).
If there are asymptomatic abnormalities, what is the trigger for such lab testing to be performed to find the MGUS?
Clinicians do not order these tests to identify MGUS: MGUS can be considered an "incidental" finding. We don't know what triggers these test orders, nor do we require a reason from the ordering clinician. Some of the protein electrophoresis tests may be ordered in patients with liver or renal disease, immune deficiencies, or infections. Others may be ordered to investigate symptoms that suggest a clinically significant plasma cell disease, but the monoclonal protein may be unrelated to the anemia, hypercalcemia, or renal impairment.