[Enzymatic assay of creatinine in serum: comparison with Jaffé methods (author's transl)].

The creatinine concentrations in 337 sera were determined by enzymatic assay and by six different modifications of the Jaffé method. The enzymatic assay showed satisfactory precision and gave the same results as the assay after adsorption on Fuller's earth (Lloyd's reagent). All other methods using picrate gave falsely high values: the relative deviation from the enzymatic method had a median value between +20% and +50% for creatinine concentrations in the range 22-88 mu mol/l, and between +10% and 30% for creatinine concentrations in the range 89-177 mu mol/l. The study thus confirms the lack of specificity of all Jaffé methods, with the exception of the assay after adsorption on Fuller's earth.