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Work-up for abdominal pain, epigastric tenderness, nausea, and vomiting. An enzyme with molecular weight of 45 to 55 kilodaltons, urinary amylase is used in the differential diagnosis of pancreatitis. It is very useful in diagnosis of pseudocyst of the pancreas, where the urine amylase may remain elevated for weeks after the serum amylase has returned to normal, after a bout of acute pancreatitis.
Macroamylasemia is characterized by high serum amylase but normal urine amylase. The amylase:creatinine ratio remains useful for the diagnosis of macroamylasemia, but its nonspecificity has otherwise left it with few other applications. In macroamylasemia the clearance is very low.1
Unlike serum amylase, urine amylase levels are normal with renal failure. While serum amylase usually returns to normal within three to five days, without complications urine amylase is increased longer than serum amylase in acute pancreatitis. Two-hour collections are more practical and provide results sooner than longer collections.
The major test for pancreatitis additional to serum and urine amylase is serum lipase. It has good specificity and its laboratory analysis is greatly improved from the 1960s. Also, some patients with pancreatitis have very high triglyceride levels. Immunoreactive trypsin is not available stat and is not widely available at all.
1. Eckfeldt JH, Levitt MD. Diagnostic enzymes for pancreatic disease. Clin Lab Med. 1989 Dec; 9(4):731-743. PubMed 2480201
Street HV, Close JR. Determination of amylase activity in biological fluids. Clin Chim Acta. 1956 May-Jun; 1(3):256-268. PubMed 13343527
