Macroamylase: prevalence, distribution of age, sex, amylase activity, and electrophoretic mobility.

The contribution made by macroamylase to the occurrence of hyperamylasemia of unknown origin has not been previously quantitated nor has the distribution of age and sex been identified in a large sample. Knowing the pattern of this enzyme complex when analyzed by an electrophoretic isoenzyme procedure would be of importance in recognizing its presence. During a three-year period we have studied a population of 2 900 patients with elevated serum amylase from whom specimens were sent to our laboratory with a request for amylase isoenzyme analysis. It was assumed that the primary reason for requesting these analyses was to clarify the presentation of hyperamylasemia. Macroamylase occurred in 9.6% of these patients. The total activity of the macroamylase specimens was typically 1 to 4 times normal but ranged to 20 times normal. Comparing these patients with a macroamylase-negative group, the distribution of age and sex was found to be no different. Macroamylase had a characteristically unusual electrophoretic pattern with bands faster than normal pancreatic amylase in 10% of cases, bands between pancreatic and salivary in 30% of cases, and the remaining 60% with atypical anodal bands.