Aldolase is an enzyme found throughout the body, particularly in muscles. Like all enzymes, it is needed to trigger specific chemical reactions. Aldolase helps muscle turn sugar into energy. Testing for aldolase is done to diagnose and monitor skeletal muscle diseases.
Skeletal muscle diseases increase the aldolase level found in a person's blood. Skeletal muscles are those muscles attached to bones and whose contractions make those bones move. When the muscles are diseased or damaged, such as in muscular dystrophy, the cells deteriorate and break open. The contents of the cells, including aldolase, spill into the bloodstream. Measuring the amount of aldolase in the blood indicates the degree of muscle damage.
As muscles continue to deteriorate, aldolase levels decrease and eventually fall below normal. Less muscle means fewer cells and less aldolase.
Muscle weakness may be caused by neurologic as well as muscular problems. The measurement of aldolase levels can help pinpoint the cause. Aldolase levels will be normal where muscle weakness is caused by neurological disease, such as poliomyelitis or multiple sclerosis, but aldolase levels will be elevated in cases of muscular disease, such as muscular dystrophy.
Aldolase is also found in the liver and cardiac muscle of the heart. Damage or disease to these organs, such as chronic hepatitis or a heart attack, will also increase aldolase levels in the blood, but to a lesser degree.
Aldolase is measured by mixing a person's serum with a substance with which aldolase is known to trigger a reaction. The end product of this reaction is measured, and, from that measurement, the amount of aldolase in the person's serum is determined.
The test is covered by insurance when medically necessary. Results are usually available the next day.
To collect the 5-10 ml of blood needed for this test, a healthcare worker ties a tourniquet on the patient's upper arm, locates a vein in the inner elbow region, and inserts a needle into that vein. Vacuum action draws the blood through the needle into an attached tube. Collection of the sample takes only a few minutes.
The patient should avoid strenuous exercise and have nothing to eat or drink, except water, for eight to ten hours before this test.
Discomfort or bruising may occur at the puncture site and the person may feel dizzy or faint. Pressure to the puncture site until the bleeding stops will reduce bruising. Warm packs to the puncture site will relieve discomfort.
Newborns have the highest normal aldolase levels and adults the lowest. Normal values will vary based on the laboratory and the method used.
As noted, aldolase is elevated in skeletal muscle diseases, such as muscular dystrophies. Duchenne's muscular dystrophy, the most common type of muscular dystrophy, will increase the aldolase level more than any other disease.
Nondisease conditions that affect the muscle, such as injury, gangrene, or an infection, can also increase the aldolase level. Also, strenuous exercise can temporarily increase a person's aldolase level.
Certain medications can increase the aldolase level, while others can decrease it. To interpret what the results of the aldolase test mean, a physician will evaluate the result, the person's clinical symptoms, and other tests that are more specific for muscle damage and disease.
A Manual of Laboratory and Diagnostic Tests. 5th ed. Ed. Francis Fishback. Philadelphia: Lippincott, 1996.
Garza Diana, and Kathleen Becan-McBride. Phlebotomy Handbook. 4th ed. Stamford: Appleton & Lange, 1996.
Henry, John B., ed. Clinical Diagnosis and Management by Laboratory Methods. 19th ed. Philadelphia: W. B. Saunders Co., 1996.
Mayo Medical Laboratories. Interpretive Handbook. Rochester, MN: Mayo Medical Laboratories, 1997.
Nancy J. Nordenson
Aldolase—An enzyme, found primarily in the muscle, that helps convert sugar into energy.
Enzyme—A substance needed to trigger specific chemical reactions.
Neurologic—Having to do with the nervous system.
Skeletal muscle—Muscle connected to, and necessary for the movement of, bones.