Indirect Bilirubin

0.2 - 0.9 mg/dl

Bilirubin is the main bile pigment in humans, which when increased causes the yellow discolouration of skin and eyes called Jaundice . Bilirubin is taken from the blood, processed (conjugated to make it water soluble ) by the liver , and then excreted into bile by the liver . 

Serum Bilurubin is generally considered as a true test of LFT , since it reflects the livers true ability to take up, process and secrete Bilirubin into the bile. 

Two forms of Bilirubin are:

1. Direct Bilirubin ( Conjugated Bilirubin) 
2. Indirect Bilirubin ( UnConjugated Bilirubin) 

Total Bilirubin = Indirect Bilirubin + Direct Bilirubin

Bilirubin production and ecxretion follows a specific pathway . When the reticulo endothelial system breaks down old red blood cells, bilirubin is one of the waste products . This free bilirubin is in a lipid soluble form that must be made water soluble to be excreted.

The free or unconjugated bilirubin is carried by albumin to the liver , where it is converted or conjugated and made water soluble .Once it is conjugated into a water soluble form , bilirubin can be excreted in the urine .

An enzyme glucuronyl transferase , is necessary for the conjugation of Bilirubin . Either a lack of this enzyme or the presence of drugs that interfere with it impairs the livers ability to conjugate bilirubin . 

The term Direct and Indirect reflect the way the two types of bilirubin react to certain dyes . Conjugated bilirubin is water soluble and reacts directly when dyes are added to the blood specimen. The non soluble , free bilirubin does not react to the reagents until alcohol is added to the solution , thus the measurement of this type of bilirubin is indirect .

• Both Direct and Indirect Bilirubin is elevated in Hepatitis
• Elevated Indirect Bilirubin is a feature of Haemolytic anaemia

When there is s/s of jaundice, have anaemia , have h/o heavy drinking , have cirrhosis, 

When there are symptoms like weakness , fatigue , nausea , vomiting , dark urine , light coloured stools , pruritus, diarrhoea

• Erythroblastosis foetalis
• Haemolytic anaemia
• Physiological jaundice
• Sickle cell anaemia
• Transfusion reaction
• Hepatitis 
• Liver disease
• Cirrhosis
• Liver tumor
• Gilberts syndrome
• Epstein barr virus
• Cytomegalo virus
• Dubin Johnson syndrome 
• Congestive heart failure
• Pulmonary Infarction
• Pulmonary Embolus