Extent of bilirubin interference with Beckman creatinine methods

Abstract

The aim of the study was to determine the extent of bilirubin interference on two different Beckman–Coulter creatinine methods used on the CX5 PRO/DxC 600 and the DxC 800 systems, respectively. The Beckman methods were compared with a high-performance liquid chromatography (HPLC) method using 104 patient samples with creatinine concentrations μmol/L and bilirubin concentrations of between 30 and 802 μmol/L. The linear regression analysis calculations expressing the relationship between bilirubin concentration and the observed difference between the Beckman and HPLC creatinine methods are: DxC800 creatinine M (modular or cup) method: r² 0.217, slope −0.023 and intercept 6.43; and DxC600 method: r² 0.7324, slope −0.0882 and intercept 12.01. There is significantly greater interference by bilirubin on the CX5 PRO/DxC 600 method, which can lead to inaccuracy in the calculation of the estimated glomerular filtration rate by the Modification of Diet in Renal Disease equation.