Which finding on electrophoresis is most suggestive of a monoclonal gammopathy requiring further immunofixation?

• A. A sharp M-spike on serum protein electrophoresis.
• B. A diffuse gamma band across the entire region.
• C. No gamma region detected.
• D. A normal protein electrophoresis pattern.

Answer: (A)

A discrete, narrow monoclonal spike in the gamma region on serum protein electrophoresis signals a single clone producing one specific immunoglobulin. This pattern is the hallmark of a monoclonal gammopathy and is the finding that most strongly prompts immunofixation to identify the exact heavy/light chain type and confirm clonality.

In contrast, a diffuse gamma region reflects polyclonal gammaglobulins from many different clones, a lack of gamma region means no detectable gamma globulins, and a normal pattern shows no abnormal spike. Because a sharp M-spike points to a single immunoglobulin being overproduced, it best indicates monoclonality and the need for further immunofixation to classify the protein and assess clinical significance.