Why are autoantibodies not often detected on monoclonal gammopathy assays (SPEP/IFE, quantitiative immunoglobulins)?

Autoantibodies do not cause a false positive M protein. Even though autoantibodies may target a specific antigen, they are polyclonal. Rarely, a very high rheumatoid factor titer can produce a broad-based (polyclonal) peak in the electrophoretic pattern.

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