Alanine aminotransferase (ALT) and aspartate aminotransferase (EST) are intracellular enzymes in hepatocytes.
ALT exists exclusively in the cytoplasm.
AST is found in the cytoplasm and mitochondria.
AST is present in muscles, the kidneys, and the brain.
ALT is more specific for hepatocellular injury.
The normal serum AST: ALT ratio is approximately 1.
Serum aminotransferase is activity is determined by spectrophotometric assays that measure light intensity is solution and may be impaired by lipemia, hemolysis, or marked bilirubinemia.
The AST/ALT ratio is the ratio between the concentrations of the enzymes aspartate transaminase (AST) and alanine transaminase (ALT) in the blood.
Known as De Ritas ratio.
Generally, the cutoff value is 1.24: with levels 1.24 or above the the ratio AST/ALT is high, and <1.24 ratio is low.
It is sometimes useful in medical diagnosis to differentiate between causes of liver damage, or hepatotoxicity.
Most causes of liver cell injury are associated with a greater increase in ALT than AST.
Metabolic risk factors of obesity in hypertension are associated with higher ALT levels and the median ALT and AST levels increase with body mass index, likely due to non-alcoholic fatty liver disease.
An AST to ALT ratio of 2:1 or greater is suggestive of alcoholic liver disease, particularly in the setting of an elevated gamma-glutamyl transferase.
The AST to ALT ratio can also occasionally be elevated in a liver disease pattern in patients with nonalcoholic steatohepatitis, and it is frequently elevated in an alcoholic liver disease pattern in patients with hepatitis C who have developed cirrhosis.
Patients with Wilson’s disease or cirrhosis due to viral hepatitis may have an AST that is greater than the ALT, though the ratio typically is not greater than two.
Many liver diseases, such as viral hepatitis or autoimmune hepatitis are associated with elevated AST and ALT due to hepatocyte membrane damage with subsequent release of enzymes into the blood.
Aminotransferase levels are generally mild to moderately increased at one and a half to 5× the upper limit of normal, in non-alcohol related fatty liver disease, chronic viral hepatitis, acute Budd-Chiari syndrome, acute fatty liver of pregnancy, alcohol related hepatitis, and cirrhosis.
Patients with alcohol related hepatitis often have serum AST: ALT ratios greater than or equal to two.
cirrhosis is typically associated with the AST: ALT ratio greater than 1 reflecting reduced hepatocyte production of ALT and impaired clearance of AST by liver sinusoidal cells.
When the AST is higher than ALT, a muscle source of these enzymes should be considered.
Serum aminotransferase levels of more than five times the upper limit of normal occur: acute viral hepatitis, ischemic hepatitis. drug induced liver injury, toxin induced hepatitis, autoimmune hepatitis, HELLP syndrome or a transient biliary tree obstruction.
The AST/ALT ratio increases in liver abnormalities..
In alcoholic liver disease, the mean ratio is 1.45
The mean ratio is 1.33 in post necrotic liver cirrhosis.
The mean ratio is greater than 1.17 in viral cirrhosis.
The mean ratio is greater than 2.0 in alcoholic hepatitis.
The mean ratio is 0.9 in non-alcoholic hepatitis.
The mean ratio is greater than 4.5 in Wilson disease or hyperthyroidism.
Muscle inflammation due to dermatomyositis may cause AST>ALT.
AST and ALT are not good measures of liver function because they do not reliably reflect the synthetic ability of the liver and they may come from tissues other than liver.
The magnitude of AST and ALT elevations vary depending on the cause of the hepatocellular injury.
Alcoholic fatty liver disease: AST > 8 times normal and ALT > 5 times normal.
Nonalcoholic fatty liver disease: AST and ALT > 4 times normal.
Acute viral hepatitis or toxin-related hepatitis with jaundice: AST and ALT > 25 times normal.
Ischemic hepatopathy (ischemic hepatitis, shock liver): AST and ALT > 50 times normal and in addition the lactate dehydrogenase is often markedly elevated.
Chronic hepatitis C virus infection: Wide variability, typically normal to less than twice normal, rarely more than 10 times normal.
Chronic hepatitis B virus infection: Levels fluctuate; the AST and ALT may be normal, though most patients have mild to moderate elevations.
The ratio is an independent predictor of patient survival in chronic hepatic disease and solid organ malignancies