Liver function tests: Difference between revisions

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AST exists in two [[isoenzymes]] namely mitochondrial form and cytoplasmic form. It is found in highest concentration in the liver, followed by heart, muscle, kidney, brain, pancreas, and lungs.<ref name=":0">{{Cite book|title=Harrison's principles of internal medicine |isbn=9781259644047|edition= Twentieth |___location=New York|oclc=990065894|last1 = Kasper|first1 = Dennis L.|last2=Fauci|first2=Anthony S.|last3=Hauser|first3=Stephen L.|last4=Longo|first4=Dan L.|last5=Larry Jameson|first5=J.|last6=Loscalzo|first6=Joseph|date=2018-02-06}}</ref> This wide range of AST containing organs makes it a relatively less specific indicator of liver damage compared to ALT. An increase of mitochondrial AST in bloods is highly suggestive of tissue [[necrosis]] in [[myocardial infarction]] and chronic liver disease. More than 80% of the liver AST activity are contributed by mitochondrial form of the isoenzymes, while the circulating AST in blood are contributed by cytoplasmic form of AST. AST is especially markedly raised in those with [[liver cirrhosis]].<ref name="Shivaraj 2009"/> AST can be released from a variety of other tissues and if the elevation is less than two times the normal AST then, no further workup needs to be performed if a patient is proceeding to surgery.{{cn|date=November 2021}}

In certain pregnancy related conditions such as hyperemesis gravidarum, AST can reach as high as 73 IU/L, 66 IU/L in pre-eclampsia, and 81 IU/L in HELLP syndrome.<ref name="Shivaraj 2009"/>

===AST/ALT ratio===