Amylase, isoamylase and macroamylase.

Hyperamylasaemia has long been regarded as pathognomonic of acute pancreatitis. However, recent work has revealed a number of conditions where a gross elevation may be an incidental finding, notably diabetic ketoacidosis. The recent discovery of 'macroamylase', a high molecular weight amylase-protein complex capable of producing hyperamylasaemia with low urine amylase, has further complicated diagnosis and has led to the introduction of the ratio of amylase clearance to creatinine clearance as a diagnostic aid. Serum amylase may be resolved, by most electrophoretic media, into bands which correspond to those obtained when pancreatic homogenates or saliva are electrophoresed. The initial promise of this technique has not been realised at the routine diagnostic level. Duodenal juice amylase has been the classical enzyme used in assessing exocrine pancreatic function and although it is still of value it is being amplified by other enzyme tests.