ALT is commonly measured clinically as part of
liver function tests and is a component of the
AST/ALT ratio. When used in diagnostics, it is almost always measured in international units/liter (IU/L) or
μkat. While sources vary on specific reference range values for patients, 0-40 IU/L is the standard reference range for experimental studies. When elevated ALT levels are found in the blood, the possible underlying causes can be further narrowed down by measuring other enzymes. For example, elevated ALT levels due to
hepatocyte damage can be distinguished from bile duct problems by measuring
alkaline phosphatase. Also, myopathy-related elevations in ALT should be suspected when the aspartate transaminase (AST) is greater than ALT; the possibility of muscle disease causing elevations in liver tests can be further explored by measuring muscle enzymes, including
creatine kinase. Many drugs may elevate ALT levels, including
zileuton,
omega−3-acid ethyl esters (Lovaza), anti-inflammatory drugs, antibiotics, cholesterol medications, some antipsychotics such as risperidone, and anticonvulsants.
Paracetamol (acetaminophen) may also elevate ALT levels. For years, the
American Red Cross used ALT testing as part of the battery of tests to ensure the safety of its blood supply by deferring donors with elevated ALT levels. The intent was to identify donors potentially infected with hepatitis C because no specific test for that disease was available at the time. Prior to July 1992, widespread blood donation testing in the US for hepatitis C was not carried out by major blood banks. With the introduction of second-generation
ELISA antibody tests for
hepatitis C, the Red Cross changed the ALT policy. , donors previously disqualified for elevated ALT levels and no other reason may be reinstated as donors when they contact the donor-counseling department of their regional Red Cross organization. In 2000, the American Association for Clinical Chemistry determined that the appropriate terminology for AST and ALT are aspartate aminotransferase and alanine aminotransferase. The term transaminase is outdated and no longer used in liver disease.
Low ALT Low plasma ALT can be a marker of low
muscle mass and is associated with
frailty,
sarcopenia,
disability, as well as increased mortality in the elderly population. In patients with
inflammatory bowel disease, low ALT is associated with a more active disease. == See also ==