In vitro test for the quantification of direct bilirubin in human serum and plasma in Roche / Hitachi cobas c systems.
Bilirubin is formed in the reticuloendothelial system during the degradation of aging erythrocytes. The heme portion of hemoglobin and other heme-containing proteins is cleaved, is metabolized to bilirubin and transported to the liver as a complex with serum albumin. In the liver, bilirubin is coupled to glucuronic acid to dissolve and then
transported through the bile duct and excreted through the digestive tract. In diseases or conditions in which hemolysis processes produce bilirubin faster than the rate at which
can be metabolized in the liver, there is an increase in circulating levels of unconjugated (indirect) bilirubin. Immaturity of the liver and some other diseases, in which the bilirubin coupling mechanism is reduced, cause correspondingly increased levels of unconjugated bilirubin in the circulation. Bile duct obstruction or damage to the hepatocellular structure causes an increase in circulating levels of conjugated (direct) and unconjugated (indirect) bilirubin.