The AST/ALT ratio is the ratio between the concentrations of the enzymes aspartate transaminase (AST) and alanine transaminase (ALT) in the blood of a human or animal. It is measured with a blood test and is sometimes useful in medical diagnosis to differentiate between causes of liver damage, or hepatotoxicity.
Most causes of liver cell injury are associated with an AST that is lower than the ALT. However, 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. In addition, 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.
When the AST is higher than ALT, a muscle source of these enzymes should be considered. For example, muscle inflammation due to dermatomyositis may cause AST>ALT. This is a good reminder that 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 (such as muscle).
Magnitude of AST and ALT elevations
The magnitude of AST and ALT elevations vary depending on the cause of the hepatocellular injury [16-19]. While values may vary between individuals, the following are typical AST and ALT patterns relating to the "upper limit of normal" (ULN):
- Alcoholic fatty liver disease: AST <8 times the ULN; ALT <5 times the ULN
- Nonalcoholic fatty liver disease: AST and ALT <4 times the ULN
- Acute viral hepatitis or toxin-related hepatitis with jaundice: AST and ALT >25 times the ULN
- Ischemic hepatopathy (ischemic hepatitis, shock liver): AST and ALT >50 times the ULN (in addition the lactate dehydrogenase is often markedly elevated)
- Chronic hepatitis C virus infection: Wide variability, typically normal to less than twice the ULN, rarely more than 10 times the ULN
- Chronic hepatitis B virus infection: Levels fluctuate; the AST and ALT may be normal, though most patients have mild to moderate elevations (approximately twice the ULN); with exacerbations, levels are more than 10 times the ULN
|Na+ = 140||Cl− = 100||BUN = 20||/|
|Glu = 150|
|K+ = 4||CO2 = 22||PCr = 1.0||\|
|ARTERIAL BLOOD GAS:|
|HCO3− = 24||paCO2 = 40||paO2 = 95||pH = 7.40|
|pACO2 = 36||pAO2 = 105||A-a g = 10|
|Ca = 9.5||Mg2+ = 2.0||PO4 = 1|
|CK = 55||BE = −0.36||AG = 16|
|PMO = 300||PCO = 295||POG = 5||BUN:Cr = 20|
|UNa+ = 80||UCl− = 100||UAG = 5||FENa = 0.95|
|UK+ = 25||USG = 1.01||UCr = 60||UO = 800|
|PROTEIN/GI/LIVER FUNCTION TESTS:|
|LDH = 100||TP = 7.6||AST = 25||TBIL = 0.7|
|ALP = 71||Alb = 4.0||ALT = 40||BC = 0.5|
|AST/ALT = 0.6||BU = 0.2|
|AF alb = 3.0||SAAG = 1.0||SOG = 60|
|CSF alb = 30||CSF glu = 60||CSF/S alb = 7.5||CSF/S glu = 0.4|
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