Evaluation of matrix effects of reference materials in serum creatinine measurements

Abstract

Objective To evaluate the trueness of routine systems for serum creatinine measurement and the matrix effects of creafinine reference materials on the systems. Methods The Clinical and Laboratory Standards Institute (CLSI) EP14-A2 protocol was used for the study and an isotope dilution liquid chromatography tandem mass spectrometry (ID-LC/MS/MS) method was used as the comparative method. Fory fresh patient specimens, 15 EQA materials, 13 calibrators, two control materials and 8 frozen serum materials were measured by the comparative method and 15 routine systems (7 enzymatic methods and 8 alkaline picrate methods). Matrix effects were assessed by using the EP14-A2 procedure, and the trueness of the evaluated methods were assessed by comparing the results of the 40 fresh patient specimens obtained with the evaluated methods and the comparative method. Results Tweenty-nine of 30 commercial materials showed matrix effects on the alkaline picrate systems, and 13 of the commercial materials showed matrix effects on the enzymatic systems. Fresh frozen serum materials prepared at the National Center for Clinical Laboratories showed no matrix effect on all 15 routine systems. Calibration biases were observed on 8 alkaline picrate systems and some enzymatic methods. Conclusions Matrix effect, calibration bias and nonspecificity in serum creatinine measurements. Continued efforts are needed for improving the trueness and comparability of serum creatinine measurements. Key words: Creatinine; Isotope labeling; Chromatography. liquid; Tandem mass spectrometry; Picrates; Clinical enzyme tests