A simplified method for detecting macroamylasemia by measuring serum amylase activity at different reaction temperatures.

Amylase activity in serum and urine, and isoamylase, were measured in 300 patients with abdominal pain to detect cases of macroamylasemia. Of these patients, 9 had hyperamylasemia and 2 were diagnosed as cases of macroamylasemia on the basis of their amylase/creatinine clearance ratio, the gel filtration pattern of their amylase on a dextran column, and results of immunological analysis. Amylase activity in macroamylasemia is reported to show an anomalous response to increase in reaction-temperature. In this report, measurements of the temperature-activity relationships of serum amylase confirmed that the ratio of serum amylase activity at 50 degrees C to that at 25 degrees C (AMY-50 degrees C/AMY-25 degrees C ratio) in patients with macroamylasemia was higher than that in normal subjects or patients with pancreatitis. Moreover, when macromolecular amylase in the sera of patients with macroamylasemia was separated from amylase of normal molecular weight by dextran gel chromatography, it showed a significantly higher AMY-50 degrees C/AMY-25 degrees C ratio than the latter. Measurement of this AMY-50 degrees C/AMY-25 degrees C ratio seems to be a convenient and useful method for differential diagnosis of hyperamylasemia.