liver functiion tests

1. HEPATIC FUNCTION TESTS:
HEPATIC FUNCTION TESTS MANSI SHARMA M.Sc BIOCHEMISTRY 3 rd SEM ROLL NUMBER 7051
CONTENTS:
CONTENTS FUNCTIONS OF LIVER TESTS TO ASSESS HEPATIC FUNCTION MAJOR LFTS TESTS BASED ON
EXCRETORY FUNCTIONS TESTS BASED ON SERUM ENZYMES TESTS BASED ON SYNTHETIC FUNCTIONS
TESTS BASED ON DETOXIFICATION
The Function of Liver:
The Function of Liver Liver is largestand mostcomplexinternal organ All blood flow from intestine and pancreas
reaches liver via portal venous system Liver is a multifunctional organ thatis involved in diverse body functions.
Metabolic Functions Liver actively participates in carbohydrate metabolism,lipid,protein,mineral and vitamin
metabolisms.Excretory Functions Bile pigments,bile salts and cholesterol are excreted in bile into intestine.
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Protective functions & detoxification Kupffer cells of liver perform phagocytosis to eliminate foreign compounds.For
example ammonia is detoxified to urea and metabolism ofxenobiotics (detoxification).Clearance ofhormones such
as i nsulin,parathyroid hormone,oestrogen,cortisol Hematological and synthetic functions Liver participates in
formation of blood (particularlyin embryo) Synthesis of plasma proteins (albumin and prothrombin),hormones e.g a
ngiotensinogen,insulin-like growth factor and triiodothyronine.Destruction oferythrocytes (Bilirubin)
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5. Storage functions Glycogen, vitamins A, D and B 12 6. Serum enzymes Acting as markers ofliver damage
Test to assess liverfunction:
Test to assess liver function LFTs are groups ofclinical biochemistryblood assays designed to give information about
the state of liver. Liver function tests(LFT) are helpful to detect the abnormalities and extentof liver damage.LFT
assays are frequentlymore sensitive than clinical signs and symptoms .Liver is a large size factory of safety
.Therefore it can perform manyof its functions almostnormally, despite the damage.Selection of righttest is
importantin LFT. This is due to the fact that since liver participates in several functions,the functions that is
measured in LFTmay not be the one that is adverselyaffected.
MAJOR LFTs:
MAJOR LFTs Test based on excretory functions- measurementofbile pigments ,bile salts ,bromosulphthlein.Tests
based on serum enzymes derived from liver-determination oftransaminases ,alkaline phosphatase 5’-nucleotidase,
gamma glutamyl-transpeptidase.Tests based on metabolic capacity- galactose tolerance,fructose tolerance.Tests
based on synthetic functions- prothrombin time,serum albumin.Tests based on detoxification- hippuric acid
synthesis
MARKERS OF LIVER FUNCTIONS:
MARKERS OF LIVER FUNCTIONS BILIRUBIN ALANINE TRANSAMINASE ASPARTATE TRANSAMINASE
ALBUMIN PROTHROMBIN TIME UREA AMMONIA CHOLESTEROL TRIGLYCERIDES HALF LIVES OF DRUGS
BILE ACIDS
BILIRUBIN:
BILIRUBIN It is a bile pigment,and is the excretory end productof heme degradation.It is conjugated in liver to form
bilirubin diglucouronide ,and excreted in bile . All the excretory function tests are based on bilirubin concentrations in
the body .
Tests based on excretory functions:
Tests based on excretory functions 1. I cterus index A simple testthatmeasure the yellow color of serum due to
bilirubin.This method is crude and outdated.However this is often helpful in rapid assessmentofneonatal jaundice.
VAN DER BERG REACTION:
VAN DER BERG REACTION Principle of this test is the reaction between sulfanilic acid (sulfanilic acid in HCl and
sodium nitrate) with bilirubin Aforementioned reaction forms a purple colored complex,azobilirubin.Conjugated
bilirubin produces purple color immediatelyon mixing with reagentThis response is known van den Bergh as direct
positive Unconjugated bilirubin gives purple color onlyon addition ofalcohol This response is called as indirect

2. positive If both, conjugated and unconjugated bilirubin,are presentin increased amounts,a purple color is produced
immediately.The purple color,so obtained,is intensified on adding alcohol.The reaction is called biphasic
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If it is indirectpositive then it may indicate hemolytic jaundice.If it is direct positive then it may indicate obstructive
jaundice.If it is biphasic then itmay indicate hepatic jaundice .
Urine urobilinogen:
Urine urobilinogen Normally,trace amounts ofurobilinogen are presentin urine.In case of complete destruction,no
urobilinogen is found in urine,because bilirubin is unable to enter the intestine.In hemolytic jaundice,increased
production of bilirubin leads to an increase in urine . Thus increasedconc. of urobilinogen in urine and absence
of bilirubin in urine are strongly suggestive of hemolytic jaundice .
Faecal urobilinogen:
Faecal urobilinogen Normal quantityof urobilinogen excreted in faeces per day is 50-250 mg.Faecal urobilinogen
increases in hemolytic jaundice in which dark colored reaction faeces are passed.Faecal urobilinogen is decreased
or is absentif there is obstruction to flow of bile as in obstructive jaundice.Complete absence offaecal urobilinogen is
stronglysuggestive ofmalignantobstruction .
Bromosulphthalein test:
Bromosulphthalein testInjected bromosulphthalein is excreted by liver through bile and function of liver is tested by
its ability to excrete the dye. In healthy human beings,<15% ofthe dye should be retained after 25 minutes and 5%
after45 minutes.In parenchymatous liver diseases ,excretion proceeds more slowly.In advanced liver cirrhosis ,
removal is very slow and 40-50% of the dye is retained after 45 minutes.
ROSE-BENGAL DYE TEST:
ROSE-BENGAL DYE TEST Rose bengal dye is another dye used to assess excretoryfunction. 10 ml of a 1%
solution ofthe dye is injected IV slowly. Normally50% or more of the dye disappears within 8 minutes.In
parenchymatous liver diseases high count in the neck persists and there is hardlyrise in the count over abdomen,as
the dye is retained.
Tests based on metabolicactivities:
Tests based on metabolic activities Galactose tolerance testGalactose is converted into glucose in the liver and its
tolerance is useful as a liver function test. Galactose is given orally and blood glucose is determined after definite
intervals.Galactose index is obtained by adding the blood galactose levels atdifferentintervals. Upper limitof 160 is
normal.In liver diseases,very high values are obtained.In infective and toxic hepatitis,values above 500 are
observed.
Fructose tolerance test:
Fructose tolerance testFructose is given to fasting patient.Fasting blood sugar is estimated in samples taken athalf
hourly intervals for two and half hours after taking oral fructose.Normally,there is no rise in blood sugar levels.In
infective hepatitis and parenchymatous liver cell damage,a rise in blood sugar level than that in fasting is observed.
Test based on change in plasma protein:
Test based on change in plasma protein TURBIDITY TESTS Turbidity tests reflect both qualitative and quantitative
changes in plasma proteins.The qualitative change in turbidity tests is due to increase in gamma globulin.THYMOL
TURBIDITY TEST- Normal range for thymol turbidity test is 0-3 maclagan units/100 ml ofserum.In infective hepatitis,
thymol turbidity is observed to be maximum immediatelyafter the onsetof jaundice,butremain high for several
weeks.ZINC SULFATE TURBIDITY TEST- Normal range is 0-6 maclagan units/100ml ofserum.Higher values are
observed in cirrhosis ofliver. It may be positive in other cases where there is increase in gamma globulin .
Tests based on serum enzymes derivedfrom liver:
Tests based on serum enzymes derived from liver Transaminases or aminotransferases Activity of 2 enzymes -
namelyserum glutamate pyruvate transaminase(alanine transaminase)and serum glutamate oxaloacetate
transaminase(aspartate transaminase) are widelyused to assess the liver function. ALT is a cytoplasmic enzyme
while AST is found in both cytoplasm and mitochondria.Activity of these enzymes is low in normal serum.Serum ALT
and AST are increased in liver damage.ALT is more sensitive and reliable for assessmentofLFT. Estim ation of
these two cannotidentify the cause ofdamage .

3. Alkaline phosphatase :
Alkaline phosphatase ALP is mainlyderived from bone and liver. A rise in serum ALP usuallyassociated with
elevated serum bilirubin is a indicator ofbiliary obstruction.ALP is also elevated in cirrhosis and hepatic tumors.Liver
is not the sole source ofALP. Therefore should be carefullydone before coming to any conclusion.
Gamma Glutamyl Transpeptidase:
Gamma Glutamyl T ranspeptidase S pecific to liver. M ost sensitive marker than ALP, elevated with minor levels of
liver dysfunction. It also help in identifying the cause of an isolated elevation in ALP.
5’ NUCLEOTIDASE:
5’ NUCLEOTIDASE It is another test specific for cholestasis in which bile cannotflow from liver to duodenum.It also
finds out aboutdamage to the intra or extrahepatic biliarysystem.It is used as a substitute of Gamma Glutamyl
Transpeptidase.LATATE DEHYDROGENASE This is the enzyme found in many body tissues including the liver.
Increase in lactate dehydrogenase shows liver damage.
Tests based on syntheticfunctions:
Tests based on synthetic functions Serum albumin Albumin is solelysynthesized in liver. It has a half life of about20-
25 days , therefore it is a good marker to assess chronic liver damage.Decrease in serum albumin indicates severe
liver damage.2. Prothrombin time Prolonged prothrombin time indicates liver damage.
Tests based on detoxification- hippuricacid synthesis :
Tests based on detoxification- hippuric acid synthesis Itis the test for assessing the detoxification function of liver. 6
grams ofsodium benzoate is dissolved in 250 ml water and orally given to the subject, after a light breakfastand
emptying the bladder.Urine collections are made for next 4 hours and the amountof hippuric acid is estimated.
Healthy persons excrete 60% of sodium benzoate in urine.Decrease in hippuric acid excretion indicates liver
damage.
Disadvantage:
Disadvantage Rarelysuggesta specific diagnosis