Conflicting results between electrophoresis methods of serum M‐proteins

The quantification of monoclonal immunoglobulins by protein electrophoresis has been helpful in determining the prognosis for the patient. In a 65‐year old man with documented IgG λ monoclonal gammopathy, a discrepancy in the detection and quantification of this M‐protein was found when studied by four different electrophoretic methods. On a high‐resolution agarose method with acid violet staining a prominent peak was seen in the fast γ‐region. A lower resolution agarose method using an amido black staining showed a small mid‐γ restriction, and no spike was detected by high‐resolution or lower resolution capillary zone electrophoresis. The discrepancy was not attributable to a migration in the β‐region leading to masking by transferrin or C3 peak, incorrect separation on CZE due to a high isoelectric point (p I > 8.5) or pentamerization of IgM M‐proteins. Therefore, other causes for discrepancies should be investigated.