Liver Blood Tests (cont.)
Siamak T. Nabili, MD, MPH
Dr. Nabili received his undergraduate degree from the University of California, San Diego (UCSD), majoring in chemistry and biochemistry. He then completed his graduate degree at the University of California, Los Angeles (UCLA). His graduate training included a specialized fellowship in public health where his research focused on environmental health and health-care delivery and management.
William C. Shiel Jr., MD, FACP, FACR
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
In this Article
- What are the basic functions of the liver?
- What are common liver blood tests?
- What are the aminotransferases?
- Normally, where are the aminotransferases?
- What are normal levels of AST and ALT?
- What do elevated liver tests (AST and ALT) mean?
- Does AST and ALT measurements indicate liver function?
- Which blood tests are done to detect liver function?
- What are some common reasons for abnormal liver tests?
- What medications can cause abnormal aminotransferase levels?
- What conditions can cause very high aminotransferase levels?
- What are some of the less common causes of elevated liver blood tests?
- How are healthy people evaluated for mild to moderate rises in aminotransferase levels?
- How about monitoring liver blood tests?
- What about the other liver enzymes?
- Hepatitis Slideshow Pictures
- Take the Alcohol Quiz
- Alcohol Abuse Slideshow Pictures
How are healthy people evaluated for mild to moderate rises in aminotransferase levels?
Evaluation of healthy individuals with abnormal liver enzymes needs to be individualized. A health care practitioner may ask for the individual's blood test data from old records for comparison. If no old records are available, the health care practitioner may repeat blood tests in weeks to months to see whether these abnormalities persist. In the meantime, the health care practitioner will search for potential causes of liver disease such as medications or alcohol. Moreover, risk factors for hepatitis B and C, including sexual exposures, history of blood transfusions, injectable drug use, and occupational exposure to blood products will be examined. A family history of liver disease may raise the possibility of inherited diseases such as hemachromatosis, Wilson's disease, or alpha-1-antitrypsin deficiency.
A complete list of routine medications including over-the-counter medications needs to be reviewed as well. A complete physical examination by the health care practitioner is another important part of the evaluation of abnormal liver tests.
The pattern of liver enzyme abnormalities can sometimes provide useful as clues to the cause of the liver disease. For example, the majority of people with alcoholic liver disease have enzyme levels that are not as high as the levels reached with acute viral hepatitis, and frequently the AST tends to be above the ALT. Thus, in alcoholic liver disease, AST is usually under 300 units/liter while the ALT is usually under 100 units/ liter.
If alcohol or medication is responsible for the abnormal liver enzyme levels, stopping alcohol or the medication (under a health care practitioner's supervision only) should bring the enzyme levels to normal or near normal levels in weeks to months. If obesity is suspected as the cause of fatty liver, weight reduction of 5% to 10% should also bring the AST and ALT liver blood tests to normal or near normal levels.
If abnormal liver enzymes persist despite abstinence from alcohol, weight reduction, and stopping certain suspected drugs, other tests can be performed to help diagnose possible treatable liver diseases. The blood can be tested for the presence of hepatitis B and C virus and their related antibodies. Blood levels of iron, iron saturation, and ferritin (another measurement of the amount of iron stored in the body) are usually elevated in individuals with hemachromatosis. Blood levels of a substance called ceruloplasmin are usually decreased in people with Wilson's disease. Blood levels of certain antibodies (anti- nuclear antibody or ANA, anti-smooth muscle antibody, and anti-liver and kidney microsome antibody) are elevated in individuals with autoimmune hepatitis.
Ultrasound and CT scan of the abdomen are sometimes used to exclude tumors in the liver or other conditions such as gallstones or tumors obstructing the ducts that drain the liver.
Liver biopsy is a procedure where a needle is inserted through the skin over the right upper abdomen to obtain a thin strand of liver tissue for examination under a microscope. This procedure is oftentimes performed after ultrasound study has located the liver. Not everybody with abnormal liver enzymes needs a liver biopsy. The doctor will usually recommend this procedure if:
- The information obtained from the liver biopsy will likely be helpful in
planning treatment
- The doctor needs to know the extent and severity of liver
inflammation/damage
- Effectiveness of a certain treatment requires close monitoring at the
tissue level
- No obvious cause of elevated liver tests has been found despite thorough investigation
Liver biopsy is most useful in confirming a diagnosis of a potentially treatable condition. These potentially treatable liver diseases include chronic hepatitis B and C, hemachromatosis, Wilson's disease, autoimmune hepatitis, and alpha-1-antitrypsin deficiency.
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