[Misleadingly high amylase and pancreatic amylase activity in the plasma of patients with macroamylasemia].
A man aged 68 years with choledocholithiasis and cholangitis, with no clinical signs suggestive of acute pancreatitis and with a low excretion of amylase in the urine, showed persistent hyperamylasaemia which appeared to be caused by macroamylasaemia. The macroamylase (an IgA-lambda-amylase complex) accounted for nearly all (90%) of the amylase activity in the serum. The activity of pancreatic amylase in serum, determined by an immunoinhibition test which selectively blocks salivary amylase activity, constituted 99% of the amylase activity in serum (normal reference range 19-71). We showed, however, that complexed salivary amylase is not inhibited in the test, resulting in a falsely-increased activity of pancreatic amylase in serum. We conclude that macroamylasaemia can lead to a clinically misleading increase in the activity of pancreatic amylase in serum.