Our liver secretes a substance known as bile that is essential for the metabolism of fat. This bile contains a brownish yellow pigment known as bilirubin. This test estimates the amount of bilirubin in the blood. Bilirubin is produced during breakdown of red blood cells in the liver. Bilirubin is thrown out of the body through feces. In fact, it is what gives stool its natural brown color. This pigment circulates in the blood in direct as well as in indirect form.
Indirect bilirubin is the unconjugated form, which does not dissolve in water. It travels through the bloodstream to the liver, where it is converted into soluble bilirubin. Direct bilirubin is the conjugated form that is soluble in water. Jaundice, caused due to high bilirubin levels in the blood, is a condition in which the skin and whites of the eyes appear yellow. If there is too much bilirubin in the blood of a newborn baby, it may lead to brain damage, hearing loss, eye muscle disorders, and physical abnormalities.
The bilirubin test is performed to evaluate the functioning of the liver. Raised levels of bilirubin are usually indicative of liver diseases such as hepatitis or cirrhosis. Conditions in which rapid destruction of red blood cells is taking place (as in hemolytic anemia or hemolytic disease of newborns) can lead to an increase in the levels of unconjugated bilirubin. Blockage of the bile duct due to a gallstone or a tumor in the pancreas can also lead to the same. this is medically known as obstructive jaundice. Doing this test can help decide whether neonatal jaundice in an infant needs treatment or not, because if the problem is mild, it usually subsides on its own.
Adults are advised not to eat or drink for at least four hours prior to undergoing the test. Children generally do not require any special preparation before the test. In the case of infants, the blood sample is collected from the heel of the baby. The skin over the heel is cleaned at first with alcohol and then punctured using a sterile lancet. A few drops of blood are collected into a small tube. The area is then bandaged after collecting enough blood. Some pressure is applied over the punctured site to arrest bleeding quickly. The blood sample is collected from a vein in the case of grownups.
The normal values for the bilirubin test may vary from lab to lab, depending upon the equipment used and their calibration.In adults, the total bilirubin level ranges between 0.3 and 1.0 milligrams per deciliter (mg/dL). While the level of direct bilirubin ranges between 0.1 and 0.3 mg/dL, that of indirect bilirubin ranges between 0.2 and 0.7 mg/dL. If there is increased production or decreased elimination of bilirubin, high levels of bilirubin are observed in the blood. Inflammation of the gallbladder, or cholecystitis, and certain inherited enzyme deficiencies may decrease the elimination of bilirubin. A prematurely born baby may have an immature liver that cannot eliminate bilirubin properly. So, such a baby has greater chances of developing jaundice as compared to a full term baby.
Following blood collection, a small bruise may develop at the heel of the infant. Babies with bleeding disorders may continue to bleed for longer. Adults could be at risk of developing the complications that are generally associated with any blood test. Caffeine may lower bilirubin levels and thereby alter the accuracy of the test. Avoiding food for a long period of time (fasting) normally increases the level of indirect bilirubin. In rare cases, inflammation of the vein, known as phlebitis, may develop after collection of the blood sample.
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