The AST/ALT ratio is the ratio between the concentrations of the enzymes aspartate transaminase (AST) and alanine transaminase, aka alanine aminotransferase (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 a greater increase in ALT than AST; 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 when other sources may increase AST or ALT, 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|
- Nyblom H, Berggren U, Balldin J, Olsson R (2004). "High AST/ALT ratio may indicate advanced alcoholic liver disease rather than heavy drinking". Alcohol Alcohol. 39 (4): 336–9. doi:10.1093/alcalc/agh074. PMID 15208167.
- Nyblom H, Björnsson E, Simrén M, Aldenborg F, Almer S, Olsson R (September 2006). "The AST/ALT ratio as an indicator of cirrhosis in patients with PBC". Liver Int. 26 (7): 840–5. doi:10.1111/j.1478-3231.2006.01304.x. PMID 16911467. Archived from the original on 2013-01-05.
- Gopal DV, Rosen HR (February 2000). "Abnormal findings on liver function tests. Interpreting results to narrow the diagnosis and establish a prognosis". Postgrad Med. 107 (2): 100–2, 105–9, 113–4. doi:10.3810/pgm.2000.02.869. PMID 10689411.
- "Serum gamma-glutamyl transpeptidase and chronic alcoholism. Influence of alcohol ingestion and liver disease". Dig Dis Sci. 30 (3): 211–4. Mar 1985. doi:10.1007/bf01347885. PMID 2857631.
- "Ischemic hepatitis: widening horizons". Am J Gastroenterol. 87 (7): 831–6. Jul 1992. PMID 1615936.
- "Ischemic hepatitis: clinical and laboratory observations of 34 patients". J Clin Gastroenterol. 26 (3): 183–6. Apr 1998. doi:10.1097/00004836-199804000-00007. PMID 9600366.
- "Hypoxic hepatitis: clinical and hemodynamic study in 142 consecutive cases". Medicine (Baltimore). 82 (6): 392–406. Nov 2003. doi:10.1097/01.md.0000101573.54295.bd. PMID 14663289.
- Lok AS, McMahon BJ (February 2007). "Chronic hepatitis B". 45 (2): 507–39. doi:10.1002/hep.21513. PMID 17256718.
- Kenneth D. McClatchey (2002). Clinical laboratory medicine. Lippincott Williams & Wilkins. pp. 288–. ISBN 978-0-683-30751-1. Retrieved 21 May 2010.
- De Ritis F, Coltorti M, Giusti G (July 2006). "An enzymic test for the diagnosis of viral hepatitis: the transaminase serum activities. 1957". Clin. Chim. Acta. 369 (2): 148–52. doi:10.1016/j.cca.2006.05.001. PMID 16781697.