Comparison of three types of analyzers for urine protein-to-creatinine ratios in dogs

Abstract

Background: Quantitation of urine protein is important in dogs with chronic kidney disease. Various analyzers are used to measure urine protein-to-creatinine ratios (UPCR). Objectives: This study aimed to compare the UPCR obtained by three types of analyzers (automated wet chemistry analyzer, in-house dry chemistry analyzer, and dipstick reading device) and investigate whether the diferences could afect clinical decision process. Methods: Urine samples were collected from 115 dogs. UPCR values were obtained using three analyzers. Bland-Altman and Passing Bablok tests were used to analyze agreement between the UPCR values. Urine samples were classifed as normal or proteinuria based on the UPCR values obtained by each analyzer and concordance in the classifcation evaluated with Cohen's kappa coefcient. Results: Passing and Bablok regression showed that there were proportional as well as constant diference between UPCR values obtained by a dipstick reading device and those obtained by the other analyzers. The concordance in the classifcation of proteinuria was very high (K = 0.82) between the automated wet chemistry analyzer and in-house dry chemistry analyzer, while the dipstick reading device showed moderate concordance with the automated wet chemistry analyzer (K = 0.52) and in-house dry chemistry analyzer (K = 0.53). Conclusions: Although the urine dipstick test is simple and a widely used point-of-care test, our results indicate that UPCR values obtained by the dipstick test are not appropriate for clinical use. Inter-instrumental variability may afect clinical decision process based on UPCR values and should be emphasized in veterinary practice.