Clinical Lab Handbook

Container/Tube: Green-top (heparin) MICROTAINER

Alternate Container: Red-top MICROTAINER

Specimen Volume: Full Tube

Collection Instructions: Green-top Spin down immediately in centrifuge. (Red-Top) Allow specimen to clot for 30 minutes.

Centrifuge specimens and remove the serum or plasma from the cellular material within 4 hours of collection. Protect specimen from light.

The VITROS BuBc Slide is a multilayered, analytical element coated on a polyester support. A drop of patient sample is deposited on the slide and is evenly distributed by the spreading layer to the underlying layers. Aided by caffeine and sodium benzoate in the spreading layer, Bu dissociates from albumin and migrates with Bc through the masking layer to the reagent layer. Proteins (including the albumin-bound delta bilirubin and hemoglobin), as well as lipids and lipochromes, are retained in the spreading layer. The masking layer optically blocks potentially interfering compounds trapped in the spreading layer, thereby preventing them from being measured.

In the reagent layer, Bu and Bc bind to a cationic mordant. As a result, the absorbance peaks of the bilirubin fractions are shifted, and molar extinction coefficients are significantly increased.

Bilirubin mono- and di-glucuronides, when bound to the mordant, have identical spectra and are quantitated together as Bc. In the vicinity of 400 to 420 nm, Bu and Bc have similar molar absorptivities; at 460 nm, Bu has a higher molar absorptivity than Bc. Because of these unique spectral characteristics, the reflection densities at two wavelengths, 400 and 460 nm, are used to determine the concentrations of Bu and Bc.

Jaundice has been classified as unconjugated and conjugated hyperbilirubinemia. Increased plasma-unconjugated bilirubin is commonly seen in hemolytic disorders, Gilbert’s syndrome, Crigler-Najjar syndrome, neonatal jaundice, and ineffective erythropoiesis and in the presence of drugs competing for glucuronide. Increased plasma-conjugated bilirubin occurs with hepatobiliary disorders, including intrahepatic and extrahepatic biliary tree obstruction, liver cell damage, Dubin-Johnson syndrome, and Rotor syndrome. Neonatal bilirubin, the sum of Bu and Bc, is increased in erythroblastosis fetalis (hemolytic disease of the newborn), which causes jaundice in the first two days of life. Other causes of neonatal jaundice include physiologic jaundice, hematoma/ hemorrhage, hypothyroidism, and obstructive jaundice.

Bu-Unconjugated Bilirubin

Bc-Conjugated Bilirubin

Monday through Sunday

82247-Bilirubin, total

82248-Bilirubin, direct

PROTECT FROM LIGHT