Serum creatinine and urea assays on Atellica® CH and Architect® ci4100: method comparison

Serum creatinine and urea are markers of renal function usually measured in conjunction. This study aims to evaluate the comparability of a new analyzer incorporated to our laboratory, Atellica® with the established analyzer, Architect ® ci 4100 in serum creatinine and urea assays. We ran 110 tests for creatinine and 107 for urea. In both analyzers, serum creatinine assay is based on the Jaffe reaction while urea measurement is based on the Roch-Ramel enzymatic reaction. Linear association between methods was evaluated using Pearson's correlation coefficient. Methods comparability was assessed using Passing-Bablok and Deming linear regression. Differences between analyzers were evaluated using Bland-Altman plot. For serum creatinine, regression equations are Atellica = 0.9721 x Architect - 2.7282 (Passing & Bablok) and Atellica = 0.8884 x Architect + 1.3456 (Deming). The mean difference between the two methods is -11.7 pmol/L as indicated by Bland-Altman plot. For urea, regression lines are expressed as Atellica = 1.0252 x Architect - 0.1609 (Passing-Bablok) and Atellica = 1.1424 x Architect - 0.9532 (Deming). Bland-Altman plot presented a mean difference of -0.1 mmol/L. These results could be described as a very good agreement between the two methods, the two analyzers could be used interchangeably.