Veterinary Clinical Biochemistry and Laboratory Diagnosis-II

ESTIMATION OF JAUNDICE

Van den Bergh Test:

• Estimation of serum bilirubin is based on the reaction of bilirubin with diazotized sulfanilic acid to form azobilirubin, which has a red or purple colour. This reaction was first described by Ehrlich in 1883 and the diazoo reagents is called Ehrlich diazo reagent.
• Bilirubin is present in the serum in two forms. One is unconjugated and the other is conjugated to glucuronic acid. Since the glucoronide form of bilirubin is soluble in water, it reacts readily with Ehrlich's reagent. The colour developed within one minute after the addition of the reagent is taken as a measure of conjugated bilirubin or direct bilirubin.
• Unconjugated bilirubin is not soluble in water and reacts with Ehrlich's reagent only after the addition of methanol. A reading made 10 or 20 minutes after the addition of methanol is a measure of the concentration of two forms bilirubin.(Total)
• The concentration of unconjugated bilirubin is the difference between the total concentration of bilirubin and the concentration of direct bilirubin.
• Depending upon the type of bilirubin present in plasma, conjugated or unconjugated, hyperbilirubinemia can be classified as retension hyperbilirubinemia, due to over production (unconjugated) or regurgitation hyperbilirubinemia (unconjugated), due to reflux into the blood because of biliary obstruction. 

Icteric Index

• The yellow colour of serum or plasma is due to the presence of bilirubin, Icteric Index is a measure of the intensity of the yellow colour of serum by comparing with the standard potassium dichromate solution. (1.0 in 10,000 parts of water. The normal value will be less than 5 units.