Amylase

The blood amylase test is used to help diagnose and monitor acute pancreatitis. It is often ordered along with a lipase test. It may also be used to diagnose and monitor chronic pancreatitis and other disorders that may involve the pancreas.

A urine amylase test may also be ordered.Typically, its level will mirror blood amylase concentrations, but both the rise and fall will occur later.Sometimes a urine creatinine clearance may be ordered along with the urine amylase to help evaluate the ratio of amylase to creatinine that is filtered by the kidneys. This ratio is used to assess kidney function because improper function can result in a slower rate of amylase clearance.

In certain cases, for example when there is an accumulation of fluid in the abdomen (ascites), an amylase test may be performed on peritoneal fluid to help make a diagnosis of pancreatitis.

Amylase tests are sometimes used to monitor treatment of cancers involving the pancreas and after the removal of gallstones that have caused gallbladder attacks.

A blood amylase test may be ordered when a person has symptoms of a pancreatic disorder, such as:

• Severe abdominal or back pain
• Fever
• Loss of appetite
• Nausea

A urine amylase test may be ordered along with or following a blood amylase test.One or both may also be ordered periodically when a health practitioner wants to monitor a person to evaluate the effectiveness of treatment and to determine whether amylase levels are increasing or decreasing over time.

A high amylase level in the blood may indicate the presence of a condition affecting the pancreas.

In acute pancreatitis, amylase in the blood often increases to 4 to 6 times higher than the highest reference value, sometimes called the upper limit of normal.The increase occurs within 4 to 8 hours of injury to the pancreas and generally remains elevated until the cause is successfully treated.Then the amylase values will return to normal in a few days.

In chronic pancreatitis, amylase levels initially will be moderately elevated but often decrease over time with progressive pancreas damage. In this case, levels returning to normal may not indicate that the source of damage has been resolved. The magnitude of increase in amylase level does not indicate severity of pancreatic disease.

Amylase levels may also be significantly increased in people with pancreatic duct obstruction and pancreatic cancers.

In general, urine amylase levels rise in proportion to blood amylase levels and will stay elevated for several days after blood levels have returned to normal.

An increased level of amylase in peritoneal fluid can occur in acute pancreatitis but may also occur in other abdominal disorders, such as obstructed intestine or decreased blood flow to the intestines (infarct).

A low amylase level in blood and urine in a person with pancreatitis symptoms may indicate permanent damage to the amylase-producing cells in the pancreas. Decreased levels can also be due to kidney disease and toxemia of pregnancy.

Increased blood amylase levels with normal to low urine amylase levels may indicate the presence of a macroamylase, a benign complex of amylase and other proteins that accumulates in the blood.

In acute pancreatitis, elevated amylase levels usually parallel lipase concentrations, although lipase levels will remain elevated longer. The lipase test is regarded as more accurate for detecting pancreatitis, particularly acute alcoholic pancreatitis, but both lipase and amylase tests are commonly ordered together when pancreatitis is suspected.

Chronic pancreatitis is often associated with alcoholism. It may also be caused by trauma or pancreatic duct obstruction or may be seen in association with genetic abnormalities such as cystic fibrosis.