Serum
amylase shows the greatest increase among the various pancreatic
enzymes that increase at the onset of
acute pancreatitis. However, the diagnostic value of the total serum
amylase activity has been questioned due to its lack of specificity. To differentiate
hyperamylasemia due to
pancreatic disease from that due to other causes, the activity of pancreatic
amylase should be determined by using a
monoclonal antibody that specifically binds to pancreatic or salivary
amylase, or by electrophoresis. The most useful and accurate method for distinguishing pancreatic from salivary-type
hyperamylasemia is
isoamylase analysis by electrophoresis. In patients with
acute pancreatitis, increase of Amylase-1 and -2 is accompanied by the appearance of Amylase-4, a minor component of the pancreatic-type isoamylases, and by disappearance of the salivary-type
isoenzymes, thereby leaving a pattern of the pancreatic
isoenzymes alone. This
pancreatitis pattern persists for about 10 days after the onset of illness. Therefore, if such a pattern is found in a patient with clinical findings suggesting
acute pancreatitis despite a normal serum
amylase level, the patient can be diagnosed as having
acute pancreatitis or a recent attack of the disease. However, the existence of an inherited trait of the
pancreatitis pattern in some healthy individuals must be borne in mind. Patients with recurrent
chronic pancreatitis also show pancreatic-type
hyperamylasemia, whereas the pancreatic
amylase activity decreases when pancreatic exocrine insufficiency progresses.
Hyperamylasemia due to elevated salivary
amylase activity is also common in patients with
diabetic ketosis or
malignancies such as
lung cancer (
adenocarcinoma).
Hyperamylasemia is also found following various types of operation. In most cases, it is salivary-type
hyperamylasemia.(ABSTRACT TRUNCATED AT 250 WORDS)