Interferencia de la bilirrubina en la medición del paracetamol por el método del indofenol en el analizador Dimension® EXL™

Abstract

BackgroundBlood levels of acetaminophen (paracetamol) are measured routinely in large acetaminophen overdoses or when poisoning is suspected, in order to predict the likelihood of hepatotoxicity. However some cases of spurious acetaminophen levels have been reported in jaundiced patients. Material and methodsThe interference of bilirubin in acetaminophen measurements was studied on the Dimension® EXL™ by preparing a primary mixture of bilirubin at 800 mg/dL, which was spiked to a quality control solution with high acetaminophen concentration in order to get a bilirrubin concentration of 40 mg/dl on the mixture. Acetaminophen concentration was measured in the mixture with bilirubin and in reference solution without bilirubin. Interference was assessed and quantified by diluting the bilirubin solution to achieve final concentrations of 20, 10, 5, 2.5, 1.25 and 0.625mg/dl (342, 171, 85.5, 42.75, 21.37 and 19.69μmol/l). A graph of the interference was obtained showing the bias of acetaminophen concentrations with reference solution vs. increasing bilirubin concentrations. ResultsAcetaminophen concentrations in both solutions followed Gaussian distributions. The t test showed significant negative interference at bilirubin concentrations higher to 5mg/dl (85.5μmol/l), which means that blood acetaminophen concentrations must be interpreted with caution in cases of hyperbilirubinemia.