Liver Function Tests Health Article

Preparation

Patients are asked to fast and to inform clinicians of all drugs, even over-the-counter drugs, that they are taking. Many times liver function tests are done on an emergency basis and fasting and obtaining a medical history are not possible.

Aftercare

Patients will have blood drawn into a vacuum tube and may experience some pain and burning at the site of injection. A gauze bandage may be placed over the site to prevent further bleeding. If the person is suffering from severe liver disease, they may lack clotting factors. The nurse or caregiver should be careful to monitor bleeding in these patients after obtaining blood.

Normal results

Reference ranges vary from laboratory to laboratory and also depend upon the method used. However, normal values are generally framed by the ranges shown below. Values for enzymes are based upon measurement at 37°C.

• ALT: 5–35 IU/L. (Values for the elderly may be slightly higher, and values also may be higher in men and in African-Americans.)
• AST: 0–35 IU/L.
• ALP: 30–120 IU/LALP is higher in children, older adults and pregnant females.
• GGT: males 2–30 U/L; females 1–24 U/L.
• LDH: 0–4 days old: 290–775 U/L; 4–10 days: 545–2000 U/L; 10 days–24 months: 180–430 U/L; 24 months–12 years: 110–295 U/L; 12–60 years: 100–190 U/L; 60 years: >110–210 U/L.
• Bilirubin: (Adult, elderly, and child) Total bilirubin: 0.1–1.0 mg/dL; indirect bilirubin: 0.2–0.8 mg/dL; direct bilirubin: 0.0–0.3 mg/dL. (Newborn) Total bilirubin: 1–12 mg/dL. Note: critical values for adult: greater than 1.2 mg/dL. Critical values for newborn (requiring immediate treatment): greater than 15 mg/dL.
• Ammonia: 10–70 micrograms per dL (heparinized plasma). Normal values for this test vary widely, depending upon the age of the patient and the type of specimen.
• Albumin: 3.2–5.4 g/L.

Abnormal results

ALT: Values are significantly increased in cases of hepatitis, and moderately increased in cirrhosis, liver tumor, obstructive jaundice, and severe burns. Values are mildly increased in pancreatitis, heart attack, infectious mononucleosis, and shock. Most useful when compared with ALP levels.

AST: High levels may indicate liver cell damage, hepatitis, heart attack, heart failure, or gall stones.

ALP: Elevated levels occur in diseases that impair bile formation (cholestasis). ALP may also be elevated in many other liver disorders, as well as some lung cancers (bronchogenic carcinoma) and Hodgkin's lymphoma. However, elevated ALP levels may also occur in otherwise healthy people, especially among older people.

GGT: Increased levels are diagnostic of hepatitis, cirrhosis, liver tumor or metastasis, as well as injury from drugs toxic to the liver. GGT levels may increase with alcohol ingestion, heart attack, pancreatitis, infectious mononucleosis, and Reye's syndrome.

LDH: Elevated LDH is seen with heart attack, kidney disease, hemolysis, viral hepatitis, infectious mononucleosis, Hodgkin's disease, abdominal and lung cancers, germ cell tumors, progressive muscular dystrophy, and pulmonary embolism. LD is not normally elevated in cirrhosis.

Bilirubin: Increased indirect or total bilirubin levels can indicate various serious anemias, including hemolytic disease of the newborn and transfusion reaction. Increased direct bilirubin levels can be diagnostic of bile duct obstruction, gallstones, cirrhosis, or hepatitis. It is important to note that if total bilirubin levels in the newborn reach or exceed critical levels, exchange transfusion is necessary to avoid kernicterus, a condition that causes brain damage from bilirubin in the brain.

Ammonia: Increased levels are seen in primary liver cell disease, Reye's syndrome, severe heart failure, hemolytic disease of the newborn, and hepatic encephalopathy.

Albumin: Albumin levels are increased due to dehydration. They are decreased due to a decrease in synthesis of the protein which is seen in severe liver failure and in conditions such as burns or renal disease that cause loss of albumin from the blood.

Patient education

Health-care providers should inform the patient of any abnormal results and explain how these values reflect the status of their liver disease. It is important to guide the patient in ways to stop behaviors such as taking drugs or drinking alcohol, if these are the causes of the illness.

BOOKS

Burtis, Carl A. and Edward R. Ashwood. Tietz Textbook of Clinical Chemistry. Philadelphia: W. B. Saunders, 1999.

Cahill, Matthew. Handbook of Diagnostic Tests. 2nd ed. Springhouse, PA: Springhouse Corporation, 1999.

Henry, J. B. Clinical Diagnosis and Management by Laboratory Methods. 20th ed. Philadelphia: W. B. Saunders, 2001.

Wallach, Jacques. Interpretation of Diagnostic Tests. 7th ed. Philadelphia: Lippincott Williams & Wilkins, 2000.

OTHER

Jensen, J. E. Liver Function Tests. [cited April 4, 2003]. <http://www.gastromd.com/lft.html>.

National Institutes of Health. [cited April 4, 2003]. <http://www.nlm.nih.gov/medlineplus/encyclopedia.html>.

Worman, Howard J. Common Laboratory Tests in Liver Disease. [cited April 4, 2003]. <http://www.cpmcnet.columbia.edu/dept/gi/labtests.html>.

Jane E. Phillips, Ph.D.
Mark A. Best, M.D.