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{{Short description|
{{Redirect|LFTs||LFT (disambiguation){{!}}LFT}} {{Use dmy dates|date=June 2020}}
{{Infobox interventions |
| Name = S.G.O.T. (ALT), S.G.P.T. (AST)
| Image =
| Caption = Liver function and its markers raised in different conditions
| ICD10 = K-70 to K-77
| ICD9
| MeshID = D008111
|
▲ MedlinePlus = 003436 |
}}
'''Liver function tests''' ('''LFTs''' or '''LFs'''), also referred to as a hepatic panel or liver 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)]] 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|url-access=subscription}}</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.{{ ==Standard liver panel==
Standard liver tests for assessing liver damage include alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP). Bilirubin may be used to estimate the excretory function of the liver and coagulation tests and albumin can be used to evaluate the metabolic activity of the liver.<ref name="Shivaraj 2009"/>
Although example reference ranges are given, these will vary depending on method of analysis used at the administering laboratory, as well as age, gender, ethnicity, and potentially unrelated health factors. Individual results should always be interpreted using the reference range provided by the laboratory that performed the test.<ref>{{citation |url=https://www.testing.com/articles/laboratory-test-reference-ranges/#:~:text=A%20normal%20result%20in%20one,this%20website%2C%20Testing.com. |title=Laboratory Test Reference Ranges |website=Testing.com |access-date=15 December 2024}}</ref>
===Total bilirubin===
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Measurement of total [[bilirubin]] includes both unconjugated (indirect) and conjugated (direct) bilirubin. Unconjugated bilirubin is a breakdown product of [[heme]] (a part of [[hemoglobin]] in red blood cells). The liver is responsible for clearing the blood of unconjugated bilirubin, by 'conjugating' it (modified to make it water-soluble) through an enzyme named [[UDP-glucuronyl-transferase]]. When the total bilirubin level exceeds 17 μmol/L, it indicates liver disease. When total bilirubin levels exceed 40 μmol/L, bilirubin deposition at the sclera, skin, and mucous membranes will give these areas a yellow colour, thus it is called [[jaundice]].<ref name="Shivaraj 2009">{{cite journal|display-authors=3|last1=Shivaraj|first1=Gowda|last2=Prakash|first2=B Desai|last3=Vinayak|first3=V Hull|last4=Avinash|first4=AK Math|last5=Sonal N|first5=Venekar|last6=Shruthi S|first6=Kulkarni|title=A review on laboratory liver function tests|journal=The Pan African Medical Journal|date=22 November 2009|volume=3|issue=17|pages=17|pmid=21532726|pmc=2984286}}</ref>
The increase in predominantly unconjugated bilirubin is due to overproduction, reduced hepatic uptake of the unconjugated bilirubin and reduced conjugation of bilirubin. Overproduction can be due to the reabsorption of a [[haematoma]] and ineffective [[erythropoiesis]] leading to increased red blood cell destruction. [[Gilbert's syndrome]] and [[Crigler–Najjar syndrome]] have defects in the [[UDP-glucuronyl-transferase]] enzyme, affecting bilirubin conjugation.<ref name="Shivaraj 2009"/>
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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|publisher=McGraw Hill LLC|___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.{{
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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[[Alkaline phosphatase]] (ALP) is an enzyme in the cells lining the [[biliary tract|biliary ducts]] of the liver. It can also be found on the mucosal epithelium of the small intestine, [[proximal convoluted tubule]] of the kidneys, bone, liver, and placenta. It plays an important role in lipid transposition in small intestines and calcification of bones. 50% of all the serum ALP activities in blood are contributed by bone. Acute viral hepatitis usually has normal or increased ALP. For example, hepatitis A has increased ALP due to [[cholestasis]] (impaired bile formation or bile flow obstruction) and would have the feature of prolonged itching. Other causes include: infiltrative liver diseases, granulomatous liver disease, abscess, [[amyloidosis]] of the liver and [[peripheral arterial disease]]. Mild elevation of ALP can be seen in liver cirrhosis, hepatitis, and [[congestive cardiac failure]]. Transient [[hyperphosphataemia]] is a benign condition in [[infant]]s, and can reach normal level in 4 months. In contrast, low levels of ALP is found in [[hypothyroidism]], [[pernicious anemia]], [[zinc deficiency]], and [[hypophosphatasia]].<ref name="Shivaraj 2009"/>
ALP activity is significantly increased in the third trimester of [[pregnancy]].<ref name="Gronowski2004" /> This is due to increased synthesis from the [[placenta]] as well as increased synthesis in the [[liver]] induced by large amounts of estrogens.<ref name="Gronowski2004" /><ref name="McCombBowersPosen1979">{{cite book | title = Alkaline Phosphatase | last1 = McComb | first1 = Robert B. | last2 = Bowers | first2 = George N. | last3 = Posen | first3 = Solomon | chapter = Clinical Utilization of Alkaline Phosphatase Measurements | date = 1979 | pages = 525–786 | publisher = Springer US | doi = 10.1007/978-1-4613-2970-1_9 | isbn = 978-1-4613-2972-5 | url = }}</ref><ref name="pmid14236214">{{cite journal | vauthors = Mueller MN, Kappas A | title = Estrogen pharmacology. I. The influence of estradiol and estriol on hepatic disposal of sulfobromophthalein (BSP) in man | journal = J Clin Invest | volume = 43 | issue = 10| pages = 1905–14 | date = October 1964 | pmid = 14236214 | pmc = 289635 | doi = 10.1172/JCI105064 | url = }}</ref> Levels in the third trimester can be as much as 2-fold greater than in non-pregnant women.<ref name="Gronowski2004">{{cite book | title = Handbook of Clinical Laboratory Testing During Pregnancy | last1 = Gronowski | first1 = Ann M. | chapter = Human Pregnancy | date = 2004 | pages = 1–13 | publisher = Humana Press | doi = 10.1007/978-1-59259-787-1_1 | isbn = 978-1-4684-9862-2 | url = }}</ref> As a result, ALP is not a reliable marker of hepatic function in pregnant women.<ref name="Gronowski2004" /> In contrast to ALP, levels of ALT, AST, GGT, and [[lactate dehydrogenase]] are only slightly changed or largely unchanged during pregnancy.<ref name="Gronowski2004" /> [[Bilirubin]] levels are significantly decreased in pregnancy.<ref name="Gronowski2004" />
In pregnancy conditions such as hyperemesis gravdirum, ALP levels can reach 215 IU/L, meanwhile, in pre-eclampsia, ALP can reach 14 IU/L, and in HELLP syndrome ALP levels can reach 15 IU/L.<ref name="Shivaraj 2009"/>
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| 3.5 to 5.3 g/dL
|}
[[Albumin]] is a protein made specifically by the liver, and can be measured cheaply and easily. It is the main constituent of total protein (the remaining constituents are primarily [[globulins]]). Albumin levels are decreased in chronic liver disease, such as [[cirrhosis]]. It is also decreased in [[nephrotic syndrome]], where it is lost through the urine. The consequence of low albumin can be edema since the intravascular [[oncotic pressure]] becomes lower than the extravascular space. An alternative to albumin measurement is prealbumin, which is better at detecting acute changes (half-life of albumin and prealbumin is about 2 weeks and about 2 days, respectively).<ref>{{Cite journal|last=Smith|first=Susan H.|date=April 2017|title=Using albumin and prealbumin to assess nutritional status|url=https://dx.doi.org/10.1097%2F01.NURSE.0000511805.83334.df|journal=Nursing2021|language=en-US|volume=47|issue=4|pages=65–66|doi=10.1097/01.NURSE.0000511805.83334.df|pmid=28328780|s2cid=45694428 |issn=0360-4039|url-access=subscription}}</ref><ref>{{Cite web|title=Prealbumin Blood Test: MedlinePlus Medical Test|url=https://medlineplus.gov/lab-tests/prealbumin-blood-test/|access-date=2021-02-25|website=medlineplus.gov|language=en}}</ref>
== Other tests ==
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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).{{
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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===Lactate dehydrogenase===
[[Lactate dehydrogenase]] (LDH) is found in many body tissues, including the liver. Elevated levels of LDH may indicate liver damage.<ref>{{Cite web|title=Lactate Dehydrogenase (LDH) Test: MedlinePlus Medical Test|url=https://medlineplus.gov/lab-tests/lactate-dehydrogenase-ldh-test/|access-date=2021-02-25|website=medlineplus.gov|language=en}}</ref> LDH isotype-1 (or cardiac) is used for estimating damage to cardiac tissue, although troponin and creatine kinase tests are preferred.<ref>{{cite journal |vauthors=Nageh T, Sherwood RA, Harris BM, Byrne JA, Thomas MR | title = Cardiac troponin T and I and creatine kinase-MB as markers of myocardial injury and predictors of outcome following percutaneous coronary intervention | journal = International Journal of Cardiology | volume = 92 | issue = 2–3 | pages = 285–293 | year = 2003 | pmid = 14659867 | doi = 10.1016/S0167-5273(03)00105-0 }}</ref>
==See also==
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* [http://labtestsonline.org/understanding/analytes/liver-panel/tab/test Liver Function Tests] at Lab Tests Online
* [http://www.mayoclinic.com/health/liver-function-tests/MY00093 Overview] at [[Mayo Clinic]]
* [http://www.patient.co.uk/showdoc/40024562 Abnormal Liver Function Tests] {{Webarchive|url=https://web.archive.org/web/20120411143612/http://www.patient.co.uk/showdoc/40024562 |date=11 April 2012 }}
* [http://liverenzymes.net Overview of liver enzymes]
* [http://liverlearning.aasld.org/aasld/2016/FOLD/119140/aasld.html Abnormal Liver Tests Curriculum] at [[AASLD]]
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{{Blood tests}}
{{Authority control}}
[[Category:Liver function tests| ]]
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