Liver Function Tests

Functions of liver Test based on this function Excretory Function:Bilepigments, bile salts and other organic anions like BSP (Bromosulphthalein), Indocyanine green (ICG), Urobilinogen

Van den Bergh TestFouchets testEhrlich testBSP Excretion Test

Metabolic Functions 1. Galactose tolerance test 2. Rate of Urea synthesis3. Plasma amino acid levels

Synthetic function Serum total protein levelSerum albumin level Prothrombin time

Detoxification . Hippuric acid test

Serum enzymes 1.Transaminases2.Alkaline Phosphatase3.gamma glutamyl transpeptidase4.51 Nucleotidase5.Leucineamino peptidase

Tests based on Excretory Function• 1.Serum Bilirubin level: • Bilirubin is an endogenous anion derived from hemoglobin degradation

from the RBC. The classification of bilirubin into direct and indirect bilirubin are based on the original van der Bergh method of measuring bilirubin. Bilirubin is altered by exposure to light so

• serum and plasma samples must be kept in dark before measurements are made.

• Direct Van den bergh test• Conjugated bilirubin + Diazotised sulphanilic acid purple coloured

complex (azobilirubin). The intensity of which is measured Colorimetrically at 450 nm. Conjugated bilirubin is also called direct bilirubin or water soluble bilirubin.

• Indirect Van den bergh test• Unconjugated bilirubin + Diazotised sulphanilic acid+ Methanol purple

coloured complex (azobilirubin). The intensity of which is measured Colorimetrically at 450 nm. This estimates total Bilirubin levels (Conjugated+ Unconjugated bilirubin).

• Indirect Bilirubin == Total bilirubin – Direct bilirubin

Type of bilirubin Normal ranges Increased in type of jaundice

Conjugated bilirubin 0 to 0.2 mg/dl Obstructive jaundice or regurgitation jaundice or Post hepatic Jaundice

Unconjugated bilirubin 0.2 to 1 mg/dl Prehepatic or hemolytic Jaundice

Both Conjugated bilirubin and Unconjugated bilirubin

0.2 to 1 mg/dl Hepatic or Hepatocellular jaundice

2. Bilirubin in Urine: This is detected by Fouchets test:

Test Observation Inference

10 ml of urine + few crystals of magnesium sulphate.heat with barium chloride solutionA white ppt. of barium sulphate is formed to which bilirubin adheres if present.This is collected on to a filter paper and Fouchets reagent is added (Ferric Chloride In Trichloro acetic acid)

Bilirubin and biliverdin gets oxidized to blue or green compounds

Bilirubin is present in urine.This is seen in obstructive jaundice. and in hepatocellular jaundice.

3.Test for Urobilinogen :• Ehrlichs Test:

Test Observation Inference Type of Jaundice

10 ml of urine + 1 ml of Ehrlich reagent (dimethyl amino benzaldehyde)

a. Pink colour which persists even after 10 times dilution

b. Pink Colour not seen

1.Increased UBG

2. Decreased UBG

1.Hemolytic

2. Obstructive

4. Bile salts in urine : This is seen in Obstructive Jaundice. This is detected By

Hay’s Test.Test Observation Inference

Sprinkle some Sulphur powder to 5 ml of urine in a test tube

1. Sulphur powder floats at the top

2.sulphur powder sinks to the bottom

1.Bile salts absent

2.Bile salts Present (Obstructive Jaundice)

5. Bromosulphthalein test:

• A single dose of BSP (50 g/l) is given and the serum concentration is measured at 45 minutes and at 2 hours.

• In normal people after 45 minutes less than 5% is retained.

• Any Increase in retention time indicates Hepatocellular impairment.

Tests to assess the metabolic capacity of the liver»Galactose tolerance test:»Liver is the only organ that helps in the metabolism of

Galactose that is in its conversion to glucose, the rate limiting step is catalysed by Galactose 1 phosphate uridyl transferase..

•350 mg of glucose /kg body weight is given as 25 to 30 % solution intravenously within 3 minutes.. Galactose level in blood is measured at 10 minute intervals for 1 hour.•In normal people the half life of Galactose in blood is about 10 to 15 minutes., whereas in patients with cirrhosis and infective hepatitis it is markedly longer.Plasma amino acids:

–The amino acid profile is abnormal in hepatic coma.•The level of aromatic aminoacids is increased but the level of branched chain aminoacids is decreased.

– Thymol turbidity test:• The turbidity produced in the serum sample on adding a thymol

solution in barbitone buffer is estimated photometrically. The turbidity is increased in viral hepatitis, primary biliary cirrhosis, Multiple myeloma due to excess production of gamma globulins.

– Zinc Sulphate turbidity test• The turbidity produced in the serum sample on adding Zinc

sulphate solution in barbitone buffer is estimated photometrically. The turbidity is increased in viral hepatitis, due to excess production of gamma globul

• Tests based on synthetic function• All plasma proteins except

immunoglobulins are synthesized in the liver. therefore the measurement of serum proteins forms a reliable index of liver function.

• Serum albumin levels• Albumin level is decreased in almost all liver

diseases. A reversal of albumin globulin ratio is seen in Cirrhosis.

• This may be due to hypoalbuminemia and associated hypergammaglobulinemia.

• b) Serum total protein levels.• In chronic liver diseases serum total protein

levels are decreased.

c) Prothrombin time:• Prothrombin is synthesized in the liver and

hence forms an useful indicator of liver function.• Prolonged Prothrombin time due to vitamin K

deficiency can be ruled out by estimating • Prothrombin time before and after parenteral

administration of vitamin K.• In acute or chronic hepatocellular injury

Prolonged Prothrombin time is seen even after administration of vitamin K indicating imminent hepatic failure and a poor prognosis.

Tests based on Detoxification functions

• Hippuric acid excretion test: • Benzoic acid is converted to benzoyl Glycine (Hippuric

acid) by conjugation in the liver and is excreted in urine. This forms an important test of liver function which tests its conjugation ability.

• In normal people almost 40% of sodium benzoate is excreted in urine within 60 minutes, while the time is prolonged in patients with hepatocellular injury.

Serum enzymes as markers of Hepatobiliary disease

Enzyme Normal range Increased in

AST 0 to 40 IU/L Viral and toxic hepatitis(Highest increases)Slight elevation in Obstructive disease

ALT 0 to 40 IU/L Viral and toxic hepatitis(Highest increases)Slight elevation in Obstructive diseaseMore than AST

ALP 0 to 145 U/L Highest levels in Obstructive Liver disease.Slight elevations are seen in Parenchymal liver diseaseElevations are also seen in cirrhosis due to increase in intestinal isoenzyme

GGT 10 to 30 IU/L Increased in Chronic alcoholism

5.5’Nucleotidase 2 to 10 IU/L Increased in Hepatobiliary disease

6.Lactate dehydrogenase (LDH

0 to 400 IU/L) Hepatic parenchymal disease