Specificity Characteristics of 7 Commercial Creatinine Measurement Procedures by Enzymatic and Jaffe Method Principles

creatinine measurement procedure’s susceptibility to potentially interfering substances. METHODS: We obtained individual residual serum or plasma samples (n 365) from patients with 19 differ-ent disease categories associated with potentially inter-fering substances and from healthy controls. Addi-tional sera at 0.9 mg/dL (80 mol/L) and 3.8 mg/dL (336 mol/L) creatinine were supplemented with ace-toacetate, acetone, ascorbate, and pyruvate. We mea-sured samples by 4 enzymatic and 3 Jaffe commercially available procedures and by a liquid chromatography/ isotope dilution/mass spectrometrymeasurement pro-cedure against which biases were determined. RESULTS: Thenumberof instanceswhen3ormore results in a disease category had biases greater than the limits o