Background: Glomerular filtration rate (GFR) can be estimated using creatinine clearance or calculated formulae, methods which rely on creatinine quantification in serum. Creatinine is most frequently measured using the Jaffe method, but this is prone to interference by, for example, bilirubin, protein and ketones. Recent amendments to this assay have been made by manufacturers in an attempt to compensate for the protein interference.
Methods: We developed a novel liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the analysis of creatinine in serum, using a strong cation exchange column to give a short run time of 1.5 min and minimal ion suppression. The method had a lower limit of quantification of 5 μmol/L and the intra- and inter-assay imprecision was <5% and <7%, respectively. Serum samples (n = 182) were subsequently analysed by enzymatic, compensated Jaffe and LC-MS/MS methods and results compared.
Results: The compensated Jaffe and enzymatic methods gave similar results to the LC-MS/MS method at concentrations below 150 μmol/L. At concentrations above this value, creatinine was underestimated by both the compensated Jaffe and enzymatic methods compared with the LC-MS/MS method.
Conclusions: We have developed a novel, simple, sensitive LC-MS/MS assay for use in comparative studies or when the results of either Jaffe or enzymatic assays are in question.
