New, simple maltogenic assay for mechanized determination of alpha-amylase activity in serum and urine.

We report a new method for the mechanized determination of serum and urinary alpha-amylase by use of a continuous-flow system, based on the measurement of maltose formed by incubating the sample with amylodextrin at pH 7 and 40 degrees C. After dialysis, maltose is converted enzymatically to glucose, which is measured by Trinder's glucose oxidase-peroxidase method [J. Clin. Pathol. 22, 246 (1969)]. The reaction is linear for amylase activities up to 1400 Somogyi units/dl (2560 U/liter) and for maltose concentrations through 1500 mg/dl. No blank assay is required; consequently precision is improved and the automated system is simplified. Calibration with primary maltose standards increases accuracy and reliability. Common reducing substances in serum and urine do not interfere at their normal concentrations. There is a linear correlation between the results of this method and those of chromogenic and iodometric methods for normal and pathologic sera and urines. The chromogenic method yields significantly higher results and the iodometric method significantly lower results than this maltogenic method for elevated amylase activities. The normal range is 40-140 Somogyi units/dl (73-256 U/liter).