PRINCIPLE OF THE METHOD
Direct bilirubin (conjugated) couples with the diazo reagent in the
presence of sulfamic acid to form azobilirubin. The intensity of color
formed is proportional to the bilirubin concentration in the sample
tested. The increase of absorbance at 546 nm is directly
proportional to the direct bilirubin concentration.
CLINICAL SIGNIFICANCE
Bilirubin is caused by the degradation of hemoglobin and exists in
two forms. Unconjugated bilirubin is transported to the liver bound
by albumin where it becomes conjugated (direct) with glucuronic
acid and excreted.
Hyperbilirubinemia is the result of an increase of bilirubin in plasma.
Possible causes: Total bilirubin: Increase hemolysis, genetic,
neonatal jaundice, ineffective erythropoiesis and presence of
drugs. Direct bilirubin: Hepatic cholestasis, genetic,
hepatocellular damage.
Clinical diagnosis should not be made based on a single test result;
it should integrate clinical and other laboratory data.
STORAGE AND STABILITY
The reagents are stable until the expiry date stated on the label
when stored at 2-8ºC, protected from light and contaminations are
prevented during their use. Do not use reagents over the expiration
date.
Signs of reagent deterioration:
- Presence of particles and turbidity.
ADDITIONAL EQUIPMENT
- MINDRAY BS-120 / BS-200E Autoanalyzer.
- General laboratory equipment.
SAMPLES
Serum or plasma, free of hemolysis. Protect samples from light.
Stability of the sample: 4 days at 2-8ºC or 2 months at –20ºC.
REFERENCE VALUES
Direct bilirubin 0 – 0,2 mg/dL (0 – 3,42 mol/L)
These values are for orientation purpose; each laboratory should
establish its own reference range.
QUALITY CONTROL
Control sera are recommended to monitor the performance of
assay procedures: SPINTROL H Normal and Pathologic (Ref.
1002120 and 1002210). If control values are found outside the
defined range, check the instrument, reagents and calibrator for
problems.
Each laboratory should establish its own Quality Control scheme
and corrective actions if controls do not meet the acceptable
tolerances.
