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Monitoring Monoclonal Gammopathies



Relationship of Serum Agarose Electrophoresis M-spike and Ig Quantitation

Slide 1

November 2009

We have compared electrophoretic and nephelometric quantitation of monoclonal proteins. And in this slide, you can see that the relationships are dependent on the heavy chain isotype. IgA monoclonal proteins yield a good relationship with a slope of 1. That is, the IgA M-spike correlates well with IgA by nephelometry. IgM also yields a linear relationship, but nephelometric results are 80% higher than IgM M-spikes. And lastly, IgG monoclonal proteins do not have a linear relationship. We believe that the nonlinearity is due to gel saturation when IgG M-spikes are >3 g/dL.

This has led us to conclude that although serum protein electrophoresis M-spikes are better for monitoring most monoclonal proteins, nephelometric quantitation is probably better for large M-spikes. In addition, as has been known for a long time, because quantitation is different by the 2 methods, clinicians should not go back and forth when monitoring patients.

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