Preparation of bilirubin standard solutions for assay calibration

Abstract Bilirubin (BR) is the product of cellular heme catabolism and the major bile pigment in animal blood. It is an established biomarker of hemolysis and liver function. In the last decade, mild hyperbilirubinemia has been shown to be a biomarker of lower cardiovascular disease risk, attributed to its antioxidant and anti-inflammatory effects. To use bilirubin as a predictive biomarker, new powerful methods are currently being developed for its direct analysis in human blood. To harmonize the different methods, it is essential to use high-quality BR standard solutions for assay calibration. We present here a protocol for the preparation of stable standard solutions in the range of 10-9- 10-5 M BR at pH 7.4 that can facilitate a universal approach to assay calibration.