LABORATORY TESTS TOR BILIRUBIN



The van den Bergh reaction is the most com­monly used test for bilirubin in biological fluids. When carried out in an aqueous medium, the test shows a colored reaction only with watersoluble bilirubin derivatives (called the direct van den Bergh fraction). The addition of methanol enables a colored reaction to take place with water-insol­uble bilirubin (called the indirect van den Bergh fraction). Direct and indirect van den Bergh frac­tions provide clinically useful estimations of con­jugated and unconjugated bilirubin, respectively, but the correlation is only a rough approximation in that levels of conjugated bilirubin are overes­timated by the direct reaction. Norma1 plasma ac­tually contains only unconjugated bilirubin.

Qualitative estimation of bilirubin in urine is carried out with Ictotest tablets or dipsticks, which are positive in cases of conjugated hyper­bilirubinemia.