Electrophoretic determination of isoamylases in serum with commercially available reagents

We describe and evaluate a method for determining isoamylases in serum. With this method, which involves conventional electrophoretic apparatus and commercially available reagents, seven isoenzymes can be resolved. The electrophoresis is performed in agarose gel, and isoenzymes are detected with a water-insoluble cross-linked starch polymer linked to a blue dye. The isoenzymes are quantified by densitometry. Within-assay imprecision (CV) was less than 7%, between-assay CV less than 11%. This method has the sensitivity to detect the major isoamylases (P2 and S2) in the serum, even at low total amylase activity. Reference intervals for P-type isoenzymes were 2-52 U/L and for S-type 2-85 U/L. P2S2 is the most common pattern found in normal individuals, then (in decreasing order) P1P2S2, P2S2S3, and P2 patterns. Patterns found in serum from cases of acute pancreatitis, mumps, macroamylasemia, and pelvic inflammatory disease are illustrated.