Bilirubin Information and Courses from MediaLab, Inc.

Two to four hours after a subarachnoid hemorrhage, the supernatant of a CSF sample will be pale pink to pale orange. The source of this color is oxyhemoglobin from lysed red cells present in the CSF before the puncture. Xanthochromia from the lysed red cells reaches its peak 24 - 36 hours after the hemorrhage and gradually disappears after four to eight days. In the same type of hemorrhage, after 12 hours yellow xanthochromia begins to appear due to the presence of bilirubin. The bilirubin is the breakdown product of oxyhemoglobin from the original lysed red cells. The yellow color in the supernatant reaches its peak in about two to four days and disappears after two to four weeks.

Xanthochromia may also be present in the cerebrospinal fluid of premature infants. Reasons for this include: elevated bilirubin in the bloodimmaturity of the blood-brain barrierelevated protein in CSF

Bilirubin, a product of hemoglobin breakdown, is characterized by its yellow pigment. The presence of bilirubin in urine is always abnormal. It is important to note that unconjugated bilirubin cannot be excreted by the kidneys because it is bound to albumin and is not soluble in water. In the liver, bilirubin combines with glucuronic acid through the action of a glucuronyl transferase to form water soluble bilirubin diglucuronide. Under normal circumstances, conjugated bilirubin passes from the bile duct and then to the intestinal tract. Intestinal bacteria reduce conjugated bilirubin to urobilinogen. Approximately half of the urobilinogen is excreted in the feces; most of the other half is recirculated through the liver. A small amount of urobilinogen bypasses the liver and is excreted in the urine.

False negative bilirubin dipstick results are often due to testing a specimen that is not fresh. Bilirubin breaks down when exposed to light. Indoxyl sulfate (Indican) can produce a yellow orange-to-red color response which may interfere with the interpretation of a positive or negative reaction. Positive nitrites due to a urinary tract infection may also cause a false negative result.

Liver damage or an obstructed bile duct allows conjugated bilirubin to enter the circulation and ultimately to appear in the urine. Patients with clinical jaundice due to hepatitis or cirrhosis will have bilirubinuria. If the jaundice is due to red cell destruction, there is an increase in unconjugated bilirubin which the kidneys cannot excrete.

Urinary urobilinogen may be increased in the presence of a hemolytic process such as hemolytic anemia. It may also be increased with infectious hepatitis, or with cirrhosis. Comparing the urinary bilirubin result with the urobilinogen result may assist in distinguishing between red cell hemolysis, hepatic disease, and biliary obstruction. Urobilinogen is increased in hemolytic disease and urine bilirubin is negative. Urobilinogen is increased in hepatic disease, and urine bilirubin may be positive or negative. Urobilinogen is low with biliary obstruction, and urine bilirubin is positive. Reagent strips methods however, cannot distinguish normal urobilinogen from absent urobilinogen, as might be seen in complete biliary obstruction.

Bilirubin is formed as a result of the breakdown of hemoglobin from erythrocytes in the reticuloendothelial system. It becomes bound to albumin and transported through the blood to the liver. This free or unconjugated bilirubin is insoluble in water and cannot be filtered through the glomerulus of the kidney. In the liver, bilirubin becomes conjugated with glucuronic acid to form bilirubin diglucuronide. This conjugated bilirubin, which is also called direct bilirubin, is water soluble and is excreted by the liver through the bile duct and into the duodenum.

Normally, small amounts of conjugated bilirubin, regurgitate back from the bile duct and enter the blood stream, so small amounts of conjugated bilirubin can be found in the plasma. Since conjugated bilirubin is not bound to protein, it is easily filtered through the glomerulus and excreted in the urine whenever the plasma level is increased. Normally, no detectable amount of bilirubin (sometimes referred to as “bile”) is found in the urine.

False positive results can occur in screening procedures for bilirubin due to color interference from large amounts of blood in the urine, very concentrated urine or drugs that discolor the urine such as Pyridium. Because of this it is important to verify positive bilirubin results with a confirmatory test such as the Ictotest®.

The reaction for the Ictotest® is based on combining a solid diazonium salt with bilirubin. When bilirubin is present, the reaction results in a blue or purple color. No other color change is considered positive.

The product profile for Ictotest® points out that bilirubin is very light sensitive, so urine specimens should be protected from excessive light exposure and examined as quickly as possible when received in the laboratory. On standing, bilirubin, which has a goldish color, is oxidized to biliverdin, which is a green color. Many of the procedures used to detect bilirubin will not react with biliverdin, so false-negative results may occur if urine is not fresh when tested.

Marcie Moore was a phlebotomist at a community hospital in Atlanta. It was her week to collect the pediatric unit and she was on her way to the room of a newborn for which she had just received orders to draw a STAT BMP (chem-7) and bilirubin. After informing the mother of the baby about the test she needed to perform, Marcie set up to perform a heel stick on the baby. Marcie chose a site on the outer edge of the heel on the bottom of the baby’s foot ( the correct area for a heel stick) and made a small incision with a Tenderfoot lancet after cleaning the site well with alcohol.She immediately began collecting the blood in the correct tube for the BMP and bilirubin. Blood flow was not strong so Marcie squeezed the baby’s foot a little to help the blood come out faster – the newborn was screaming and Marcie could tell it was making the mother uncomfortable. She wanted to hurry and get done so the mother could hold the baby.After the chemistry tech ran the blood tests on the tube, she informed Marcie that the newborn had a panic potassium level which did not coincide with the previous blood work on the newborn. Also the chemistry instrument could not perform the bilirubin due to hemolysis. Marcie was asked to recollect the specimen.

Consists of a basic metabolic panel, plus:Albumin (Alb) and Bilirubin (Bili) Alkaline Phosphatase (Alk Phos) Total protein (TP) Alanine aminotransferase (ALT) Aspartate aminotransferase (AST)

Crystals of clinical significance include leucine, tyrosine, cystine, cholesterol and bilirubin.