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Introduction ⬇

Alanine aminotransferase (ALT) is an enzyme with high concentrations found in the liver and relatively low concentrations found in the heart, muscle, and kidney.

This test is primarily used to diagnose liver disease and to monitor the course of treatment for hepatitis, active postnecrotic cirrhosis, and the effects of later drug therapy. ALT is more sensitive in the detection of liver disease than in biliary obstruction. ALT also differentiates between hemolytic jaundice and jaundice due to liver disease.

Normal Findings ⬆ ⬇

Adults:

ALT values are slightly higher in male and Black patients. Normal values vary with testing method. Check with your laboratory for reference values.

Clinical Alert

Critical ValueAlcohol–acetaminophen syndrome: Extremely abnormal ALT/aspartate transaminase (AST) values are found (>9000 U/L [>153

Procedure ⬆ ⬇

  1. Obtain a 5-mL venous blood sample (red-topped tube). Serum is needed for the test. Observe standard precautions. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered. Place the specimen in a biohazard bag.

  2. Avoid hemolysis during collection of the specimen. (ALT activity is six times higher in RBCs.)

Clinical Implications ⬆ ⬇

  1. Increased ALT levels are found in the following conditions:

    1. Hepatocellular disease (moderate to high increase)

    2. Alcoholic cirrhosis (mild increase)

    3. Metastatic liver tumor (mild increase)

    4. Obstructive jaundice or biliary obstruction (mild increase); cholecystitis

    5. Viral, infectious, or toxic hepatitis (30–50 times normal)

    6. Infectious mononucleosis

    7. Pancreatitis (mild increase)

    8. MI, heart failure

    9. Polymyositis

    10. Severe burns

    11. Trauma to striated muscle

    12. Severe shock

  2. AST/ALT comparison:

    1. Although the AST level is always increased with acute MI, the ALT level does not always increase unless there is also liver damage.

    2. The ALT is usually increased more than the AST in acute extrahepatic biliary obstruction.

    3. The AST/ALT ratio is high in alcoholic liver disease; the ALT is more specific than AST for liver disease, but the AST is more sensitive to alcoholic liver disease.

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain test purpose and blood-drawing procedure.

  2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Have patient resume normal activities.

  2. Review test results; report and record findings. Modify the nursing care plan as needed. Monitor as appropriate for liver disease.

  3. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Interfering Factors ⬆

  1. Many drugs may cause falsely increased or decreased ALT levels (see Appendix E).

  2. Salicylates may cause decreased or increased ALT levels.

  3. Therapeutic heparin causes increased ALT.

  4. Hemolyzed blood causes increases in ALT.

  5. Obesity causes increases in ALT.

Clinical Alert

There is a correlation between the presence of elevated serum ALT and abnormal antibodies to the hepatitis B virus core antigen and hepatitis C antigen. Persons with elevated ALT levels should not donate blood