Alanine transaminase

Alanine transaminase or ALT is a transaminase enzyme (EC 2.6.1.2). It is also called serum glutamate pyruvate transaminase (SGPT) or alanine aminotransferase (ALAT).

ALT is found in serum and in various bodily tissues, but is most commonly associated with the liver;

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Function

It catalyzes the transfer of an amino group from alanine to a-ketoglutarate, the products of this reversible transamination reaction being pyruvate and glutamate.

glutamate + pyruvate ⇌ α-ketoglutarate + alanine

Clinical significance

It is commonly measured clinically as a part of a diagnostic liver function test, to determine liver health. Diagnostically, it is almost always measured in units/litre (U/L).

Elevated levels

Significantly elevated levels of ALT often suggest the existence of other medical problems such as alcoholic or viral hepatitis, congestive heart failure, liver damage, biliary duct problems, infectious mononucleosis, or myopathy. For this reason, ALT is commonly used as a way of screening for liver problems. However, elevated levels of ALT do not automatically mean that medical problems exist. Fluctuation of ALT levels is normal over the course of the day, and ALT levels can also increase in response to strenuous physical exercise^[1].

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 liver-cell damage can be distinguished from biliary duct problems by measuring alkaline phosphatase. Also, myopathy-related ALT levels can be ruled out by measuring creatine kinase enzymes.

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 ("non-A non-B Hepatitis") because there was no specific test for that disease at the time. With the introduction of second generation ELISA antibody tests for Hepatitis C, the Red Cross changed the ALT policy. As of July 2003, donors previously disqualified for elevated ALT levels and no other reason may be reinstated as donors by contacting the donor counseling department of their regional Red Cross organization^[2].

See also

• Liver function tests

References

1. ^ Paul T. Giboney M.D., Mildly Elevated Liver Transaminase Levels in the Asymptomatic Patient, American Family Physician.
2. ^ Red Cross Donor Requirements