blood bilirubin test, a blood test performed in cases of jaundice to help determine whether the jaundice is caused by prehepatic causes (as with hemolytic anemia), hepatocellular dysfunction (as in hepatitis), or extrahepatic obstruction of the bile ducts (as with gallstones or tumor blocking the bile ducts). Total serum bilirubin is made up of conjugated (direct) and unconjungated (indirect) bilirubin, with varying ratios of each characterizing different diseases.
