Rapid onset monoclonal gammopathy in cutaneous lupus erythematosus: interference with complement C3 and C4 measurement

Abstract

Accurate nephelometric immunoassay requires both the analyte and the calibration standard to have the same molecular mass. Alteration in the size of the analyte can affect light scatter and yield erroneous results. We report a case where an autoantibody, a monoclonal IgM with immunoconglutinin activity, interfered with the nephelometric quantitation of plasma complement components C3 and C4.