Van den Bergh reaction

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Van den Bergh reaction is a chemical reaction used to measure bilirubin levels in blood. [1] [2] More specifically, it determines the amount of conjugated bilirubin in the blood. The reaction produces azobilirubin. Principle: bilirubin reacts with diazotised sulphanilic acid to produce purple coloured azobilirubin. [3] This reaction is highly useful in understanding the nature of jaundice. This was pioneered by the Dutch physician, Abraham Albert Hijmans van den Bergh (18691943) of Utrecht. This test helps to identify the type of jaundice. The serum of the patient is mixed with diazo reagent. If a red colour develops immediately it is called a direct positive. It happens if conjugated bilirubin is present. In an indirect positive test, the patient's serum is first treated with alcohol and later mixed with diazo reagent. This causes development of a red colour. It is seen if unconjugated bilirubin is present. If both conjugated and unconjugated bilirubin are present the reaction is termed a biphasic reaction.

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Hyperbilirubinemia is a clinical condition describing an elevation of blood bilirubin level due to the inability to properly metabolise or excrete bilirubin, a product of erythrocytes breakdown. In severe cases, it is manifested as jaundice, the yellowing of tissues like skin and the sclera when excess bilirubin deposits in them. The US records 52,500 jaundice patients annually. By definition, bilirubin concentration of greater than 3 mg/ml is considered hyperbilirubinemia, following which jaundice progressively develops and becomes apparent when plasma levels reach 20 mg/ml. Rather than a disease itself, hyperbilirubinemia is indicative of multifactorial underlying disorders that trace back to deviations from regular bilirubin metabolism. Diagnosis of hyperbilirubinemia depends on physical examination, urinalysis, serum tests, medical history and imaging to identify the cause. Genetic diseases, alcohol, pregnancy and hepatitis viruses affect the likelihood of hyperbilirubinemia. Causes of hyperbilirubinemia mainly arise from the liver. These include haemolytic anaemias, enzymatic disorders, liver damage and gallstones. Hyperbilirubinemia itself is often benign. Only in extreme cases does kernicterus, a type of brain injury, occur. Therapy for adult hyperbilirubinemia targets the underlying diseases but patients with jaundice often have poor outcomes.

References

  1. Coolidge, Thomas B. (1940). "Chemistry of the van den Bergh reaction" (PDF). Journal of Biological Chemistry. 132 (1): 119–127. doi:10.1016/S0021-9258(18)73401-7.
  2. Gray, C.H.; Whidborne, J. (6 October 1945). "Studies of the Van den Bergh reaction". The Biochemical Journal. 40 (1): 81–88. doi:10.1042/bj0400081. PMC   1258298 . PMID   16747977.
  3. Fowweather, F. S. (1932). "Bilirubin and the van den Bergh reaction" (PDF). Biochemical Journal. 26 (1): 165–182. doi:10.1042/bj0260165.