Amylase – 001396

Causes of high serum amylase include acute pancreatitis, pancreatic pseudocyst, pancreatic ascites, pancreatic abscess, neoplasm in or adjacent to pancreas, trauma to pancreas, and common duct stones.

Nonpancreatic causes of hyperamylasemia include inflammatory salivary lesions (eg, mumps), perforated peptic ulcer involving pancreas or not, intestinal obstruction and infarction, afferent loop syndrome, biliary tract disease including stones, aortic aneurysm, peritonitis, acute appendicitis, cerebral trauma, burns and traumatic shock, the postoperative state (with and without pancreatitis), diabetic ketoacidosis, and extrapancreatic carcinomas (especially of esophagus, lung, ovary). Amylase levels more than 25-fold the upper limit of normal are often found when metastatic tumors produce ectopic amylase. Such levels are higher than those usually found in cases of pancreatitis.³ In renal insufficiency amylase is usually not more than three times the upper limit of normal. Moderate increases may be reported in normal pregnancy. Increases may be found with tubo-ovarian abscess, ruptured ectopic pregnancy, macroamylasemia, and with a substantial number of drugs, including morphine. Relationships between pancreatitis and hyperlipidemias types I, IV, and V are described. Amylasemia may be associated with hyperparathyroidism.

Macroamylase is a high molecular weight material, normal amylase complexed to high molecular weight protein such as immunoglobulin. It is characterized by high serum amylase and low to normal urine amylase. Macroamylase occurs in normal as well as abnormal subjects.⁴

Other tests: In pancreatitis, varying percentages of patients have the following other abnormalities in varying combinations: elevation of triglyceride, alkaline phosphatase, AST (SGOT), total bilirubin, white blood cell count, left shift. Calcium levels should be followed in fulminant pancreatitis, since extremely low serum calcium levels can evolve. Serum lipase and two-hour urine amylase may both be extremely valuable. Although determination of serum methemalbumin has been advocated as a test for acute hemorrhagic pancreatitis, it is cumbersome and is not done in many American laboratories.

Isoenzymes of amylase exist: pancreatic and salivary type, as noted under Limitations. They can be separated by polyacrylamide gel or agarose film electrophoresis, isoelectric focusing, ion exchange chromatography, and plant isoamylase inhibitors. A monoclonal antibody approach is described.^3,5 Amylase isoenzymes are separated in few laboratories. Where available the procedure is an expensive one. It is useful in assessing the decrease of pancreatic function in cystic fibrosis, in children older than five years, who may be candidates for enzyme replacement.