Alanine Aminotransferase Test

Definition
Purpose
Demographics
Description
Preparation
Aftercare
Risks
Normal results
Abnormal results
Morbidity and mortality rates
Alternatives Resources
Precautions
Side effects
Interactions

Definition

The alanine aminotransferase test, also known as ALT, is one of a group of tests known as liver function tests (or LFTs) and is used to monitor damage to the liver.

Purpose

ALT levels are used to detect liver abnormalities. Since the alanine aminotransferase enzyme is also found in muscle, tests indicating elevated ALT levels may indicate muscle damage; however, other tests, such as the levels of the MB fraction of creatine kinase should indicate whether the abnormal test levels are because of muscle or liver damage.

Demographics

The number of ALT tests administered each year can only be estimated. Since statins are the most prescribed drugs in the United States and standards of care call for quarterly liver function tests, the number of ALTs can easily exceed 500 million per year.

Description

The alanine aminotransferase test (ALT) can reveal liver damage. It is probably the most specific test for liver damage; however, the severity of the liver damage is not necessarily shown by the ALT test since the amount of dead liver tissue does not correspond to higher ALT levels. Also, persons with normal, or declining, ALT levels may experience serious liver damage without an increase in ALT.

Nevertheless, ALT is widely used, and useful, because ALT levels are elevated in most patients with liver disease. Although ALT levels do not necessarily indicate the severity of the damage to the liver, they may indicate how much of the liver has been damaged. ALT levels, when compared to the levels of a similar enzyme, aspartate aminotransferase (AST), may provide important clues to the nature of the liver disease. For example, within a certain range of values, a ratio of 2:1 or greater for AST:ALT might indicate that a person suffers from alcoholic liver disease. Other diagnostic data may be gleaned from ALT tests to indicate abnormal results.

Preparation

No special preparations are necessary for this test.

Aftercare

This test involves blood being drawn, usually from a vein in the person’s elbow. The person being tested should keep the wound from the needle puncture covered with a bandage until the bleeding stops. Individuals should report any unusual symptoms to their physician.

Risks

The greatest risk associated with an ALT test is bleeding. The odds of experiencing uncontrolled bleeding are fewer than one in a million.

Normal results

Normal values vary from laboratory to laboratory, and should be available to physicians at the time of the test. An informal survey of some laboratories indicates many laboratories find values from approximately 7 to 50 IU/L (international units per liter) to be normal.

Abnormal results

Mildly elevated levels of ALT (generally below 300 IU/L) may indicate any kind of liver disease. Levels above 1,000 IU/L generally indicate extensive liver damage from toxins or drugs, viral hepatitis, or a lack of oxygen (usually resulting from very low blood pressure or a heart attack). A briefly elevated ALT above 1,000 IU/L that resolves in 24-48 hours may indicate a blockage of the bile duct. More moderate levels of ALT (300-1,000 IU/L) may support a diagnosis of acute or chronic hepatitis.

It is important to note that persons with normal livers may have slightly elevated levels of ALT. This is a normal finding.

Morbidity and mortality rates

Morbidity rates are excessively miniscule. The most common problems are minor bleeding and bruising. Since neither are reportable events, morbidity can only be estimated. Mortality is essentially zero.

Alternatives Resources

There are no alternatives to an alanine amino transferase test.

Precautions

The only precaution needed is to clean the venipuncture site with alcohol.

Side effects

The most common side effects of an alanine amino transferase test are minor bleeding and bruising.

Interactions

There are no known interactions with an alanine amino transferase test.

Resources

BOOKS

Fischbach, F. T. and M. B. Dunning. A Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams & Wilkins, 2008.

McGhee, M. A Guide to Laboratory Investigations, 5th ed. Oxford, UK: Radcliffe Publishing Ltd., 2008.

Price, C. P. Evidence-Based Laboratory Medicine: Principles, Practice, and Outcomes, 2nd ed. Washington, DC: AACC Press, 2007.

Scott, M. G., A. M. Gronowski, and C. S. Eby. Tietz’s Applied Laboratory Medicine, 2nd ed. New York: Wiley-Liss, 2007.

Springhouse Corp. Diagnostic Tests Made Incredibly Easy!, 2nd ed. Philadelphia: Lippincott Williams & Wilkins, 2008.

PERIODICALS

Inoue, K., M. Matsumoto, Y. Miyoshi, and Y. Kobayashi. “Elevated liver enzymes in women with a family history of diabetes.” Diabetes Research in Clinical Practice 79, no. 3 (February 2008): e4–e7.

Kansu, A. “Treatment of chronic hepatitis B in children.” Recent Patents on Anti-Infectious Drug Discoveries 3, no. 1 (January 2008): 64–69.

Lampe, E., C. F. Yoshida, R. V. De Oliveira, G. M. Lauer, and L. L. Lewis-Ximenez. “Molecular analysis and patterns of ALT and hepatitis C virus seroconversion in haemodialysis patients with acute hepatitis.” Nephrology (Carlton) 13, no. 3 (June 2008): 186–192.

Lazo, M., E. Selvin, and J. M. Clark. “Brief communication: clinical implications of short-term variability in liver function test results.” Annals of Internal Medicine 148, no. 5 (March 2008): 348–352.

OTHER

American Clinical Laboratory Association. Information about clinical chemistry. http://www.clinical-labs.org/ (February 24, 2008).

Clinical Laboratory Management Association. Information about clinical chemistry. http://www.clma.org/ (February 22, 2008).

Lab Tests Online. Information about lab tests. http://www.labtestsonline.org/ (February 24, 2008).

National Accreditation Agency for Clinical Laboratory Sciences. Information about laboratory tests. http://www.naacls.org/ (February 25, 2008).

ORGANIZATIONS

American Association for Clinical Chemistry, 1850 K Street, NW, Suite 625, Washington, DC, 20006, (800) 892-1400, http://www.aacc.org/AACC/.

American Society for Clinical Laboratory Science, 6701 Democracy Blvd., Suite 300, Bethesda, MD, 20817, (301) 657-2768, http://www.ascls.org/.

American Society for Clinical Pathology, 1225 New York Ave., NW, Suite 250, Washington, DC, 20005, (202) 347-4450, http://www.ascp.org/.

College of American Pathologists, 325 Waukegan Rd., Northfield, IL, 60093-2750, (800) 323-4040, http://www.cap.org/apps/cap.portal.

L. Fleming Fallon, Jr., M.D., Dr.P.H.

Albumin test seeLiver function tests