Liver function tests: Difference between revisions

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{{Short description|LiverBlood Functiontests Testindicating the state of the liver}}

{{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

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'''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.{{citation needed|date=May 2022}}

==Standard liver panel==

Standard liver tests for assessing liver damage include alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatasesphosphatase (APsALP). [[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 needed|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=July15 December 20202024}}</ref>

===Total bilirubin===

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Measurement of total [[bilirubin]] includes both [[Unconjugated bilirubin|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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In [[acute appendicitis]], total bilirubin can rise from 20.52 μmol/L to 143 μmol/L. In pregnant women, the total bilirubin level is low in all three trimesters.<ref name="Shivaraj 2009"/>

The measurement of bilirubin levels in the newborns is done through the use of bilimeter or transcutanoeus bilirubinometer instead of performing LFTs. When the total serum bilirubin increases over 95th percentile for age during the first week of life for high risk babies, it is known as [[hyperbilirubinemia]] of the newborn ([[neonatal jaundice]]) and requires [[light therapy]] to reduce the amount of bilirubin in the blood. Pathological jaundice in newborns should be suspected when the serum bilirubin level rises by more than 5&nbsp;mg/dL per day, serum bilirubin more than the physiological range, clinical jaundice more than 2 weeks, and conjugated bilirubin (dark urine staining clothes). [[Hemolytic disease of the newborn|Haemolytic jaundice]] is the commonest cause of pathological jaundice. Those babies with Rh hemolytic disease, ABO incompatibility with the mother, [[Glucose-6-phosphate dehydrogenase]] (G-6-PD) deficiency and minor blood group incompatibility are at increased risk of getting haemolytic jaundice.<ref>{{cite journal|last1=Sana|first1=Ullah|last2=Khaista|first2=Rahman|last3=Mehdi|first3=Hedayati|title=Hyperbilirubinemia in Neonates: Types, Causes, Clinical Examinations, Preventive Measures and Treatments: A Narrative Review Article|journal=Iranian Journal of Public Health|date=May 2016|volume=45|issue=5|pages=558–568|pmid=27398328|pmc=4935699}}</ref>

===Alanine transaminase (ALT)===

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| 3.5 to 5.3 g/dL

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[[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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* [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| ]]