Alanine aminotransferase is an enzyme involved in the transfer of an amino group from the amino acid, alanine, to alpha-ketoglutaric acid to produce glutamate and pyruvate. ALT is located primarily in liver and kidney, with lesser amounts in heart and skeletal muscle. Increased ALT activity is more specific for liver damage than increased aspartate aminotransferase (AST) activity. ALT is seldom increased in patients with heart or muscle disease in the absence of liver involvement. In healthy children, plasma ALT activity is lower than AST until 15 to 20 years of age. Thereafter, plasma ALT activity tends to be higher than AST activity until age 60, when the activities become roughly equal. The half-life of ALT in the circulation is 47 +/- 10 hours.
ALT activity in the liver is 3000 fold higher than in serum. Measurement of serum ALT activity is a good indicator of hepatocyte injury.
|Viral hepatitis||10 – 40||<1||<15||<3|
|Alcoholic hepatitis||2 – 8||>2||<15||1 – 3|
|Toxic injury||>40||>1 early||<5||>5 transient|
|Ischaemic injury||>40||>1 early||<5||>5 transient|
X ULN = times upper limit of normal, Protime prolongation is number of seconds above ULN
Patients with cirrhosis, non-alcoholic steatohepatitis, cholestatic liver disease, fatty liver and hepatic neoplasm typically have slightly raised serum ALT levels ( < 120 U/L). Patients with cirrhosis seldom have ALT levels higher than two times normal. Cirrhotic patients without ongoing liver injury the values may have normal values.
Other causes of elevated ALT include haemochromatosis, Wilson disease, autoimmune hepatitis, primary biliary cirrhosis, sclerosing cholangitis and alpha-1 antitrypsin deficiency. The medications most commonly associated with elevated ALT are sulfonamides, statins and isoniazid.
Pratt & Kaplan, NEJM 2000; 342: 1266-71 Evaluation of abnormal liver-enzyme results in asymptomatic patients
Dufour et al., Clin Chem 2000; 46: 2050-68 Diagnosis and monitoring of hepatic injury. II. Recommendations for use of laboratory tests in screening, diagnosis, and monitoring
Can be added on to an existing request up to 4 days following sample receipt
Please note this test is not UKAS accreditedSpecimen Labelling Procedure