Liver function tests: Difference between revisions

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{{Short description|Liver Function Test}}
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'''Liver function tests''' ('''LFTs''' or '''LFs'''), also referred to as a hepatic panel, are groups of blood tests that provide information about the state of a patient's [[liver]].<ref name="Lee2009">{{cite book|last=Lee|first=Mary|title=Basic Skills in Interpreting Laboratory Data|url=https://books.google.com/books?id=AUSIRcV_as0C&pg=PA259|access-date=5 August 2011|date=2009-03-10|publisher=ASHP|isbn=978-1-58528-180-0|page=259}}</ref> These tests include [[prothrombin time]] (PT/INR), [[activated Partial Thromboplastin Time|activated partial thromboplastin time]] (aPTT), [[albumin]], [[bilirubin]] (direct and indirect), and others. The liver transaminases [[Aspartate transaminase|aspartate transaminase (AST or SGOT)]] and [[Alanine transaminase|alanine transaminase (ALT or SGPT)]] <ref>{{Cite web |title=SGPT & SGOT Test: Normal Range, Levels, and What do They Indicate?

|url=https://redcliffelabs.com/myhealth/lab-test/liver-test/sgpt-sgot-test-normal-range-its-levels-and-what-do-they-indicate/ |access-date=2023-05-17 |website=Redcliffe Labs |language=en}}</ref> are useful biomarkers of liver injury in a patient with some degree of intact liver function.<ref name="pmid10221307">{{cite journal | author = Johnston DE | title = Special considerations in interpreting liver function tests | journal = Am Fam Physician | volume = 59 | issue = 8 | pages = 2223–30 | year = 1999 | pmid = 10221307 }}</ref><ref name="McClatchey2002">{{cite book|last=McClatchey|first=Kenneth D.|title=Clinical laboratory medicine|url=https://books.google.com/books?id=3PJVLH1NmQAC&pg=PA288|year=2002|publisher=Lippincott Williams & Wilkins|isbn=978-0-683-30751-1|page=288}}</ref><ref name="MengelSchwiebert2005">{{cite book|last1=Mengel|first1=Mark B.|last2=Schwiebert|first2=L. Peter|title=Family medicine: ambulatory care & prevention|url=https://books.google.com/books?id=XvLo7xvmFo0C&pg=PA268|year=2005|publisher=McGraw-Hill Professional|isbn=978-0-07-142322-9|page=268}}</ref> Most [[liver disease]]s cause only mild symptoms initially, but these diseases must be detected early. Hepatic (liver) involvement in some diseases can be of crucial importance. This testing is performed on a patient's blood sample. Some tests are associated with functionality (e.g., albumin), some with cellular integrity (e.g., [[transaminase]]), and some with conditions linked to the biliary tract ([[gamma-glutamyl transferase]] and [[alkaline phosphatase]]). Because some of these tests do not measure function, it is more accurate to call these liver chemistries or liver tests rather than liver function tests.<ref>{{Cite journal|last1=Kwo|first1=Paul Y.|last2=Cohen|first2=Stanley M.|last3=Lim|first3=Joseph K.|date=January 2017|title=ACG Clinical Guideline: Evaluation of Abnormal Liver Chemistries|url=https://dx.doi.org/10.1038%2Fajg.2016.517|journal= American Journal of Gastroenterology|language=en-US|volume=112|issue=1|pages=18–35|doi=10.1038/ajg.2016.517|pmid=27995906|s2cid=23788795|issn=0002-9270}}</ref> Several biochemical tests are useful in the evaluation and management of patients with hepatic dysfunction. These tests can be used to detect the presence of liver disease. They can help distinguish among different types of liver disorders, gauge the extent of known liver damage, and monitor the response to treatment. Some or all of these measurements are also carried out (usually about twice a year for routine cases) on individuals taking certain medications, such as anticonvulsants, to ensure that these medications are not adversely impacting the person's liver.{{cncitation needed|date=May 2022}}

==Standard liver panel==

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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, no further workup needs to be performed if a patient is proceeding to surgery.{{cncitation needed|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"/>

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===Coagulation test===

The liver is responsible for the production of the vast majority of [[coagulation]] factors. In patients with liver disease, [[international normalized ratio]] (INR) can be used as a marker of liver synthetic function as it includes [[factor VII]], which has the shortest half life (2–6 hours) of all coagulation factors measured in INR. An elevated INR in patients with liver disease, however, does not necessarily mean the patient has a tendency to bleed, as it only measures procoagulants and not anticoagulants. In liver disease the synthesis of both are decreased and some patients are even found to be hypercoagulable (increased tendency to clot) despite an elevated INR. In liver patients, coagulation is better determined by more modern tests such as [[thromboelastogram]] (TEG) or thomboelastrometry (ROTEM).{{cncitation needed|date=November 2021}}

Prothrombin time (PT) and its derived measures of prothrombin ratio (PR) and INR are measures of the [[Coagulation#Tissue factor pathway (extrinsic)|extrinsic pathway]] of [[coagulation]]. This test is also called "ProTime INR" and "INR PT". They are used to determine the clotting tendency of blood, in the measure of [[warfarin]] dosage, liver damage, and [[vitamin K]] status.<ref>{{Cite web|title=Prothrombin Time Test and INR (PT/INR): MedlinePlus Medical Test|url=https://medlineplus.gov/lab-tests/prothrombin-time-test-and-inr-ptinr/|access-date=2021-02-25|website=medlineplus.gov|language=en}}</ref>

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===Urea===

Elevated urea may indicate acute or chronic kidney disease, urinary tract obstruction, congestive heart failure, recent myocardial Infarction or gastrointestinal bleeding.{{cncitation needed|date=November 2021}}

==See also==