DETECTION OF AUTOANTIBODIES TO AMYLASE BY ELISA - COMPARISON OF DETECTION OF MACROAMYLASE AND FREE AUTOANTIBODY

New ELISAs for detecting macroamylase or free autoantibodies to amylas e were tested with 48 samples that had been characterized by gel chrom atography and electrophoresis. The macroamylase ELISA, with anti-lgG o r anti-IgA for detection, detected macroamylase in 28 of 33 samples kn own to contain macroamylase (85% sensitivity), whereas the ELISA for f ree autoantibody to amylase was positive for only II samples. Specific ities of both ELISAs were 93%. Among 28 true positives detected with t he macroamylase ELISA, 22 contained IgA, 3 contained IgG, and 3 contai ned both immunoglobulins. Detection of IgM added no true positives. EL ISA responses Cy) were proportional to log [macroamylase concentration by chromatography (x)] from 0 to 1200 U/L: y = 5.15 x + 1.66; r = 0.7 2; S-ylx = 1.65. As new tools for detecting macroenzymes consisting of enzyme-autoantibody complexes, the ELISAs show that some autoantibodi es are detected more sensitively as antibody-antigen complexes than as free antibody.