INTRODUCTION:

Liver function test is employed for accurate diagnosis, to access the severity of the damage to judge the prognosis and to evaluate therapy.

1. Test for Manufacturer and Excretion of Bile:

  • Bile is secreted by the liver, stored in the gallbladder and discrete via biliary ducts into the duodenum.
  • It consisting of biliary phospholipids, primary and secondary bile acids.
  • The test employed for synthesis and elimination of bilirubin pigment, urobilinogen and bile acids are as follows:

A) Bilirubin:-

It can be detected in serum, feces, and urine.

a. Serum Bilirubin Estimation:-

Normal value of serum Bilirubin = < 1md/dl of total bilirubin. 
Significance- Bilirubin level rises in-

  • Diseases of hepatocytes. 
  • Obstruction to biliary excretion into the duodenum.
  • In hemolysis.
  • Defects of liver uptake.
  • The conjugation of bilirubin pigment as in Gilbert’s disease.

b. In Faeces:

Assessed by inspection of stools.
Significance- Absent in biliary obstruction.

c. In urine:

Conjugated bilirubinuria in patients of hepatitis.

B) Urobilinogen:

It is normally excreted in the urine.
Significance- 

  • Increase in hepatocellular and hemolytic disease.
  • Absent in biliary obstruction.

C) Bile Acids (bile salts):

The primary bile acids formed from cholesterol in hepatocytes, which when come in contact with colonial bacteria undergo de-conjugation with the product of 2° bile.
Significance:- Increased in serum and detectable in urine in cholestasis.

2. Serum Enzyme Assays:-

Determination of certain serum enzymes is considered useful in various types of liver injury as well as in quantifying liver damage.

A. Alkaline Phosphatase:- (Range 33-96u/L)


  • It increased in hepatobiliary disease, bone disease, pregnancy. 
  • Highest in biliary obstruction.

B. Y -Glutamyl transpeptidase:-

It rises parallel alkaline Phosphatase but is specific for the hepatobiliary disease.

C.   Transaminases:- 

a) SGOT (AST):- Serum Aspartate transaminases (formerly glutamic oxaloacetic transaminase).
Normal value- 0.20 - 0.65 units/l (12 – 38 units/l)
Increased tissue injury to the liver as well as to other tissue like myocardial infarction.
 
b) Serum Alanine Transaminases (ALT):-
(formerly glutamic pyruvic transaminase) 
Normal value- 0.12 -0.70 u Kal /L (7-14 u /L )
Increased fairly specific for liver cell injury.

D. Other Enzymes:-

a. 5' Nucleotidase:- Rise parallels Alkaline Phosphatase but more specific for the disease of the hepatic organ.

b. Lactic Dehydrogenase:- Increased tumors involving in the liver.

c. Cholerineterase:- Decreased in hepatocellular disease malnutrition.

3. Test for Metabolic Function:-

The liver is the principal site of metabolism and synthesis of amino acids, protein, lipids, lipoprotein, carbohydrates, vitamins, etc.

A. Amino acids and Protein Metabolism:-

a. Serum Protein:- (Total A/G ratio, Protein electrophoresis).
Significance:- Hypoalbuminemia in hepatocellular disease.
Hyperglobulinemia in cirrhosis and chronic active hepatitis.

b. Immunoglobulins:- Not specific, alteration in IgA, IgG, IgM.

c. Clotting factors:- Prothrombin time and partial thromboplastin time prolonged in hepatocellular disease.

d. Aminoaciduria:- in fulminant hepatitis.

B. Lipid and Lipoprotein Metabolism:- 


  • Blood Lipids (i.e, total serum cholesterol, triglycerides, lipoprotein fractions).
  • Increased in cholestasis.
  • A decrease in Acute and chronic diffuse liver disease and malnutrition.

C. Carbohydrate Metabolism:-

Blood glucose and GTI:- Decreased in hepatic necrosis. 

D. Immunological Tests:-

Liver diseases are associated with the various Immunological abnormalities-

a) Non Specific Immunologic Reaction:- 


  • Smooth Muscle Antibody:- In hepatic necrosis.
  • Mitochondrial Antibody:- in 1° biliary cirrhosis.
  • Antinuclear antibody and LE cell test:- in chronic active hepatitis.

b)Antibodies to specific Etiologic agent:- 


  • Antibodies to Hepatitis B:- In hepatitis B
  • Amoeba Antibodies:- Amoebic liver asses.

E. Ancillary Diagnostic Tests:- 

a. Ultrasound Examination:-


  • Cholestasis and various etiologies.
  • SOLS, US-guided FNAC.
  • Liver biopsy.

b. FNAC / percutaneous liver Biopsy:-


  • Hepatomegaly.
  • Splenomegaly.
  • Longstanding hepatitis.
  • Unknown Cause of Hepatocellular disease.