What Is Serum Amylase?

Drue Tibbits

Serum amylase is the measure of amylase in the blood. Amylase is a digestive enzyme produced mostly by the pancreas and saliva glands. Abnormally high amounts of the enzyme may indicate a pancreatic condition such as cancer or necrosis. Conditions affecting the kidneys or liver may also result in high blood amylase results. Serum amylase tests sometimes produce falsely high readings in healthy individuals as well as normal readings in patients with pancreatic diseases.

A blood test may be done to check levels of amylase in the blood.
A blood test may be done to check levels of amylase in the blood.

Amylase builds up in the blood either because an amylase-producing organ is delivering too much of the enzyme or because the body is unable to process or excrete amylase that is normally present. The test is most often used to diagnose pancreatic disease. It also serves to monitor pancreatic function in patients with related conditions. Amylase levels may also be high in patients with inflammation or swelling of the gallbladder, obstruction of the bile duct, or peptic ulcers.

Amylase is an enzyme that breaks down starch and it is secreted in saliva.
Amylase is an enzyme that breaks down starch and it is secreted in saliva.

Some of these conditions, such as obstruction of the bile duct, cause a temporary rise of serum amylase. Gallstones can block the common bile duct, interfering with drainage of the gallbladder and liver. This can cause an increase of amylase to three times the normal level. Once the stones are passed or removed, the enzyme readings usually return to normal within 48 to 72 hours. Other conditions may cause a sustained elevation of amylase until the underlying condition receives treatment.

A low level of amylase can also be indicative of a medical condition. Low levels of the enzyme are much less common than elevated levels and may occur in toxemia of pregnancy or hepatic necrosis. Abnormal test readings, either high or low, usually result in a second test to confirm the readings. A urine amylase test may also be used to provide a wider range of diagnostic information. Liver function tests, lipase enzyme tests, and additional blood tests can help pinpoint the cause of high or low amylase levels.

The test uses blood drawn from a vein. An amylase test does not require fasting. Several medications can result in a falsely high reading, including steroids, morphine, and birth control pills. There is not a standard of values of the level of amylase that is considered normal; different laboratories use different value scales. The resultant readings of a serum amylase test should not be compared to the amylase values of a different facility.

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