Amylase and Lipase Tests

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Amylase and Lipase Tests

Definition

Amylase and lipase tests are performed to aid in the diagnosis of acute abdominal pain. Amylase and lipase are digestive enzymes made by the pancreas. Amylase affects the breakdown of starch into maltose. Lipase breaks down triglycerides, forming glycerol and fatty acids as the final product.

Purpose

Pain and abdominal tenderness associated with acute appendicitis are often difficult to distinguish from acute pancreatitis. Normal levels of amylase and lipase when measured over time exclude a diagnosis of acute pancreatitis, while one or both enzymes may be increased in acute pancreatitis. In addition to acute pancreatitis, amylase is increased with mumps, some malignancies, ectopic pregnancy, alcoholic liver disease, peptic ulcers, intestinal obstruction, and renal failure. Lipase is increased in renal failure, intestinal obstruction and liver disease. Measuring both enzymes increases diagnostic sensitivity. Acute pancreatitis is highly likely when the level of amylase in the blood plasma is more twice the normal level and lipase is increased more than fivefold normal. When amylase is increased, but lipase is normal, a nonpancreatic condition is almost always the cause. When amylase is increased more than twofold and lipase is increased but less than fivefold, renal failure, pancreatitis, intestinal obstruction, peptic ulcer disease, and acute pancreatitis are possible causes.

In acute pancreatitis, plasma amylase becomes elevated two to 12 hours after an episode of acute abdominal pain. Levels peak in 12-72 hours, usually reaching two to six times the upper limit of normal, then return to normal within four days. Lipase in blood plasma becomes abnormal four to eight hours following an episode of acute pancreatitis, reaches a peak level two to 50 times normal in approximately one day, and remains elevated for seven to 10 days.

Precautions

Blood for measurement of amylase and lipase is collected by venipuncture. The nurse or phlebotomist should follow standard precautions for the prevention of transmission of bloodborne pathogens. Amylase and lipase should not be used as screening tests for future pancreatic disease. Neither enzyme is likely to be elevated in chronic pancreatitis because enzyme production is decreased by chronic disease. Drugs that may increase amylase include morphine, phenformin, ethanol, and contraceptives. Lipase may be increased by ethanol, codeine, and narcotics. Results are dependent upon the method used and normal values may vary significantly among laboratories.

Description

Amylase and lipase tests are usually performed on a blood sample, but amylase testing can also be performed on urine. There are several methods for measuring amylase and lipase each with its own advantages and disadvantages. A common method of measuring amylase is based upon the breakdown of a synthetic glucose polymer. Urinary amylase is frequently measured using a timed urine sample. The patient should be given a urine container with instructions for collecting the urine at home. The urine should be refrigerated until it is brought to the laboratory.

Lipase is often measured using a cascade of coupling enzyme reactions that yield a colored product. The color is proportional to lipase activity.

Preparation

No special preparation is necessary for a person undergoing an amylase or lipase test.

Aftercare

Discomfort or bruising may occur at the puncture site when blood is drawn, or the person may feel dizzy or faint. To reduce bruising, pressure should be applied to the puncture site until the bleeding stops. Applying warm packs to the puncture site relieves discomfort.

Complications

Amylase and lipase tests are not associated with complications.

Results

The normal range will vary depending upon the method used and the laboratory where testing is done.

KEY TERMS

Amylase— A digestive enzyme made primarily by the pancreas and salivary glands.

Enzyme— A substance made and used by the body to speed up specific chemical reactions which might otherwise not happen, or might happen only slowly.

Lipase— A digestive enzyme made primarily by the pancreas.

Pancreatitis— Inflammation of the pancreas.

Health care team roles

A physician orders and interprets tests for amylase and lipase. A nurse or phlebotomist usually collects blood for amylase and lipase tests by venipuncture. A nurse educates the patient on the proper collection and storage of a urine sample, and may also take a drug history to identify medications which might interfere with the testing. Amylase and lipase tests are performed by a clinical laboratory scientist, CLS(NCA)/ medical technologist, MT(ASCP) or clinical laboratory technician, CLT(NCA) or medical laboratory technician, MLT(ASCP).

Resources

BOOKS

Daniels, Rick. Delmar's Manual of Laboratory and Diagnostic Tests. Albany, NY: Delmar Learning, 2003.

Fischbach, Frances Talaska, ed. Nurse's Quick Reference to Common Laboratory and Diagnostic Tests. Philadelphia: Lippincott, 2002.

Professional Guide to Diagnostic Tests. Philadelphia: Lippincott Williams and Wilkins, 2005.

Van Leeuwen, Anne M., Todd R. Kranpitz, and Lynette Smith. Davis's Comprehensive Handbook of Laboratory and Diagnostic Tests: With Nursing Implications. Philadelphia: F.A. Davis Co., 2006.