The function of the bilirubin detection kit

The conjugated bilirubin (CB) assay kit is a core tool used in clinical testing to quantitatively detect the direct bilirubin (DBil) content in blood. It accurately distinguishes conjugated bilirubin from unconjugated bilirubin (UCB) through specific chemical reactions or immunological methods, providing key basis for the diagnosis of liver and gallbladder diseases, evaluation of neonatal jaundice, and differentiation of hemolytic diseases. The following systematically explains its role from three aspects: detection principle, clinical value, and application scenarios.

1、 Detection principle and core characteristics

The principle of chemical oxidation method (diazonium salt coupling reaction): In an acidic environment with pH 3.0, conjugated bilirubin (water-soluble) reacts directly with diazonium salts (such as 2,4-dichloroaniline diazonium salts) to generate purple red azo compounds, while non conjugated bilirubin (lipophilic) needs to be accelerated by hydrolysis to a conjugated state by sodium caffeinate benzoate before color development.

Technical advantage: High specificity: Accurate separation of CB and UCB is achieved by controlling the pH value, avoiding cross interference.

Quick detection: Complete sample processing and result reading within 30 minutes, suitable for emergency testing needs.

The principle of enzymatic reaction method (peroxidase coupling): bilirubin oxidase (BOD) is used to oxidize CB to biliverdin, while releasing H ₂ O ₂, which reacts with 4-aminoantipyrine (4-AAP) and phenolic substrates to form red quinone imine under the catalysis of peroxidase (POD). The absorbance is proportional to the concentration of CB.

Technological breakthrough: Strong anti-interference ability: able to tolerate interfering substances such as lipid blood (≤ 5g/L) and hemolysis (≤ 2g/L) in the sample.

Automated adaptation: Used in conjunction with a fully automated biochemical analyzer, with a CV value of ≤ 3% (within batch) and ≤ 5% (between batches).

2、 Clinical value and diagnostic significance

Clinical significance of diagnostic threshold for abnormal manifestations of bilirubin combined with disease type

Obstructive jaundice with CB/TBl>50% CB>34.2 μ mol/L (2mg/dL) indicates complete/incomplete obstruction of the bile duct (such as cholangiocarcinoma, gallstones)

Hepatocellular jaundice CB/TBl 30% -50% CB 17.1-34.2 μ mol/L (1-2mg/dL) reflects impaired liver cell uptake and binding function (such as hepatitis, cirrhosis)

Neonatal pathological jaundice CB>25.7 μ mol/L (1.5mg/dL) - congenital diseases such as biliary atresia and neonatal hepatitis should be ruled out

Hemolytic jaundice with CB/TBl<20%, normal or mildly elevated CB to assist in distinguishing the cause of jaundice (no significant increase in CB during hemolysis)