Inaccuracy of routine creatinine measurement in canine urine

Background: Urine creatinine concentration often is used in ratios such as urine protein :creatinine to compensate for dilution orconcentration of spot urine samples. Objective: The purpose of this study was to compare the accuracy of different techniques ofurine creatinine measurement currently available for veterinary practitioners. Methods: In 104 samples of canine urine diluted1:20 with distilled water, creatinine concentration was measured using a kinetic Jaffe reaction assay, and an enzymatic techniqueon an automatic analyzer (Elimat) and 3 benchtop analyzers (Reflovet, Scil ; Vitros DT2, Ortho-Clinical Diagnostics; Vettest8008,IDEXX) used in veterinary practice. Results: The Jaffe and enzymatic techniques on the Elimat were not significantly different,and their inaccuracy tested with human control urines was 2000 mg/L. Inaccuracy was higher with multilayer slide technology systems(Vitros and Vettest) than with the Reflovet system. Results were approximately 25% and 2% lower, respectively, than with theElimat at urine creatinine concentrations about 2000 mg/L. Conclusion: Inaccuracy in urine creatinine measurements usingbenchtop analyzers should be taken into account when defining decision thresholds, which should be corrected according to themethod used to avoid misinterpretations. (Vet Clin Pathol. 2004;33:128-132)