Amylase

Normal findings

Blood ^[1]

Adult: 60-120 Somogyi units/dL or 30-220 units/L (SI units)

A slight increase in values may seen during normal pregnancy and in the elderly.

Newborn: 6-65 units/L

Urine (24-hour) ^[1]

Up to 5000 Somogyi units/24 hr or 6.5-48.1 units/hr (SI units)

Possible critical values ^[1]

Blood: Over threefold the upper limit of normal (depending on the method)

Conditions associated with high amylase levels are as follows: ^[2]

• Peptic ulcers

• Intestinal obstruction

• Pancreatic duct obstruction

• Cancer

• Gallbladder attacks

• Mesenteric thrombosis

• Postoperative abdominal surgery

• Mumps

• Macroamylasemia

• Tubal pregnancy

Conditions associated with low amylase levels are as follows:

• Liver damage

• Cystic fibrosis

• Pancreatic cancer

• Toxemia of pregnancy

The 2 tests for amylase are serum and urine. For both tests, patient should not drink alcohol for 24 hours before the test.

For the blood test, patients should not eat or drink anything except water for 2 hours before the test.

For the urine test, patients should drink enough fluids during the 24-hour test to avoid dehydration. In this test, patients should check with their physician about any medications being taken. Timed urine specimens can be obtained for urinary amylase and normalized to creatinine content.

Methods

Blood is collected into a vacuum tube via venipuncture. For urine, a patient urinates into a small container and then transfers the sample to a lab-provided larger container with a small amount of preservative. Plasma samples that have been anticoagulated with citrate or oxalate should be avoided because amylase is a calcium-containing enzyme and false low levels can be obtained with such specimens.

Notes regarding these methods are as follows:

• Keep container refrigerated.

• Do not touch inside of container or drop any foreign matter into it.

Panels

Related tests are as follows:

• Lipase test

• Urinalysis

• Urine creatinine/clearance

• Isoamylase fractionation

Description

Amylases are enzymes that catalyze the hydrolysis of amylopectin, amylose, glycogen, and their hydrolyzed products into simple and easily digestible sugars. Amylase is an enzyme produced in the pancreas and by the salivary glands that converts starches, glycogens, and related polysaccharides into simple and easily digested sugar. It is also present in molds, bacteria, yeasts, and plants.

An image depicting an amylase molecule can be seen below.

Alpha amylase is of salivary or pancreatic origin and referred to as S-type or P-type amylase, respectively. Pancreatic amylase is secreted by acinar cells of the pancreas and is tissue specific and more temperature labile than salivary amylase. Salivary amylase is synthesized by parotid, sweat, and lactating mammary glands. ^{[3, 4, 5, 6]}

On agarose gel, the mobility of the less anionic isoenzyme corresponds to pancreatic amylase, while the more anionic band is salivary amylase. Macroamylasemia is a condition of persistently elevated serum amylase activity with no apparent pancreatic disorder due to the formation of a large amylase-globulin complex, which is not excreted. ^[7]

Indications/Applications

Most elevations in serum amylase are due to increased rates of amylase entry into the blood stream, decreased rates of clearance or both. The test is primarily used, in conjunction with a lipase test, to help diagnose and monitor acute pancreatitis and other pancreatic disorders. Serum amylase increases in 6-48 hrs of onset of acute pancreatitis but not in proportion to the severity of the disease and activity returns to normal in 3-5 days. Urine amylase increases in proportion to serum amylase and remains elevated for several days after serum amylase has been normalized. The ratio of amylase urinary clearance to creatinine clearance can be used in the diagnosis of acute and relapsing pancreatitis.

Serum amylase levels can also be elevated in pancreatic cancers, although a bit too late to be diagnostically useful; however, the results can assist in monitoring treatment of pancreatic cancers. Other conditions in which determination of serum amylase is useful is to determine the effects of the removal of gallstones, and swelling and inflammation of the salivary/parotid glands.

Indications for testing are as follows: ^[8]

• Severe abdominal pain

• Fever

• Loss of appetite

• Nausea