bilirubin (total) in serum/plasma (TBIL)

Indications

• assessment of hyperbilirubinemia
  • jaundice

Reference interval

• Male & Female: 0.2 - 1.3 mg/dL

Principle

The Kodak Ektachem Clinical Chemistry Slide (TBIL) is a dry, multilayered, analytical element coated on a clear polyester support. The analysis is based on a modification of the classical diazo reaction.

The reported concentration of total bilirubin is the sum of unconjugated bilirubin (Bu), mono & di-glucuronide conjugated bilirubin(Bc), & delta bilirubin (DELB), a bilirubin fraction covalently bound to albumin.

A 10 uL drop of patient sample is deposited on the slide & is evenly distributed by the spreading layer. This layer provides a reflective background for measuring the diazo products of bilirubin & contains all reagents necessary to determine total bilirubin.

The method uses dyphlline & surfactant to dissociate unconjugated bilirubin from albumin. Unconjugated bilirubin, conjugated bilirubin & albumin-linked bilirubin (delta) subsequently react with the diazonium salt 4-(N-carboxy- methylsufamyl) benzendiazonium hexafluorophosphate to produce azobilirubin chromophores that have similar molar absorptivities and absorbance maxima around 520 nm. The buffered control layer, which is below the spreading/reaction layer, contains a polymeric quaternary amine (a mordant) coated on a transparent support. The mordant is used to stabilize the azo dyes generated in the reaction layer & to increase the sensitivity of the assay.

The concentration of total bilirubin is determined by measuring the azobilirubin chromophores at two wavelengths through the transparent support. Reflectance measurements at 540 nm & 460 nm are taken after 5 minutes incubation at 37 C. The measurement at 460 nm is used to correct for spectral interferences.

The following reaction sequences are involved:

                          Diphylline
Total Bilirubin    --------------------->          Azobilirubin
                  [4-(N-carboxy-methylsulfamyl)-   Chromophores
                   benzenediazonium hexafluoro-
                   phosphate]

Clinical significance

• total bilirubin concentration in serum or plasma
• the reported concentration of total bilirubin is the sum of
  • unconjugated bilirubin
  • mono- & di-glucuronide conjugated bilirubin
  • delta bilirubin, a bilirubin fraction covalently bound to albumin
• total serum bilirubin is increased in jaundice
  • exception of anicteric jaundice
• causes of jaundice are
  • prehepatic, resulting from various hemolytic diseases
  • hepatic, resulting from hepatocellular injury or intraheptic biliary obstruction
  • posthepatic, resulting from hepatic duct obstruction or common bile duct obstruction

Increases

• see hyperbilirubinemia
• pharmaceutical agents:
  • in vivo effects
    • see drugs that may affect liver function tests (LFTs)
    • chlordiazepoxide
    • gall bladder dyes
  • chemical interferences
    • dextran, novobiocin

Decreases

• pharmaceutical agents:
  • in vivo effects
    • phenobarbital
  • chemical interferences
    • ascorbate, caffeine, theophylline

Specimen

No special patient preparation is necessary.

Sample Preparation: Collect the specimen by standard venipuncture technique. Remove serum promptly from clot & analyze as soon as possible.

Do not use this slide for samples from neonatal patients < 14 days old.

Special precautions: Protect specimens from light; direct exposure to sunlight is reported to cause as much as a 50% loss of serum bilirubin in one hour, especially when specimen is kept in capillary tubes. Exposure to normal laboratory light can result in significant loss of serum bilirubin after 2 to 3 hours. Refrigerate specimen if it cannot be analyzed immediately. Freeze specimen for long-term storage or shipment.

Minimum sample size of 0.5 milliliters with an optimum size of 1.0 mL or larger.

More general terms

• bilirubin (total) in serum/plasma/blood

Additional terms

• Bilicheck
• bilirubin
• bilirubin (conjugated/unconjugated) in serum
• bilirubin conjugated in serum
• bilirubin unconjugated in serum (indirect bilirubin)

Component of

• chemistry 14 panel (comprehensive metabolic panel, CMP, chem 12, SMA12, SMA20)
• conjugated bilirubin/total bilirubin in serum
• bilirubin, conjugated (direct) & total in serum
• liver (function) tests (LFT, liver panel, hepatic function panel)
• hemolysis panel
• anemia panel

Patient information

bilirubin in serum patient information