Bilirubin

Bilirubin, a product of hemoglobin metabolism, is conjugated in the liver to the mono- and diglucuronides and excreted in bile. Some conjugated bilirubin is bound to serum albumin, so-called D (delta) bilirubin. Elevated serum bilirubin occurs in liver disease, biliary obstruction, or hemolysis. 

Normal Range: 0.1-1.2 Direct (conjugated to glucuronide) bilirubin, 0.1-0.4 mg/dL (< 7 µmol/L); Indirect (unconjugated) bilirubin, 0.2-0.7 mg/dL (< 12 µmol/L) mg/dL

increased in: Acute or chronic hepatitis, cirrhosis, biliary tract obstruction, toxic hepatitis, congenital liver enzyme abnormalities (Dubin-Johnson, Rotor's, Gilbert's, Crigler-Najjar syndromes), fasting, hemolytic disorders. Hepatotoxic drugs. 

 

Additional: Assay of total bilirubin includes conjugated (direct) and unconjugated (indirect) bilirubin plus delta bilirubin (conjugated bilirubin bound to albumin). It is usually clinically unnecessary to fractionate total bilirubin. The fractionation is unreliable by the diazo reaction and may underestimate unconjugated bilirubin. Only conjugated bilirubin appears in the urine and it is indicative of liver disease; hemolysis is associated with increased unconjugated bilirubin. Persistence of delta bilirubin in serum in resolving liver disease means that total bilirubin does not effectively indicate time course of resolution