Abstract: Objective To compare the results of the serum creatinine determined by isotope dilution liquid chromatography tandem mass spectrometry (ID-LC-MS/MS), sarcosine oxidase enzymatic method (enzymatic method) and Jaffe method, and provide the reference for concordance from different determination systems. Methods Serum creatinine levels in 200 clinical serum samples, 50 hemolyzed samples, 50 lipidic samples (triglyceride 1.88-17.60 mmol/L) and 6 standard serum samples were determined by ID-LC-MS/MS, enzymatic method and Jaffe method. The precisions, recoveries, relative biases and interferences to hemolysis and lipid were compared among the 3 methods. Results Adding 50 μmol/L and 100 μmol/L creatinine, the coefficients of variation (CV) were < 1.14%, < 2.39% and < 3.84%, the recoveries were 84.9%, 82.2%; 74.4%, 70.8% and 96.1%, 96.3% for enzymatic method, Jaffe method and ID-LC-MS/MS, respectively. Compared to ID-LC-MS/MS, the linearity regression equations of enzymatic method and Jaffe method were Y_{enzymatic method}=0.964X_ID-LC-MS/MS+0.385(r=0.994) and Y_{Jaffe method}=0.955X_ID-LC-MS/MS+13.14(r=0.979). Compared to ID-LC-MS/MS, the average relative bias of serum creatinine were -2.93% by enzymatic method and 13.9% by Jaffe method. Significant negative interferences were observed in hemolyzed and lipidic samples. Conclusions There is a good comparability on serum creatinine between enzymatic method and ID-LC-MS/MS. The serum creatinine level can be overestimated by Jaffe method. The serum creatinine levels can be underestimated in hemolyzed and lipidic samples by enzymatic method and Jaffe method.

Key words: Creatinine, Isotope dilution liquid chromatography tandem mass spectrometry, Sarcosine oxidase enzymatic method, Jaffe method