Comparison of urine protein-to-creatinine ratio in urine samples collected by cystocentesis versus free catch in dogs.

To assess whether urine protein-to-creatinine (UPC) ratios determined in urine samples collected by cystocentesis versus those collected by free catch provide similar diagnostic information for dogs.Evaluation study.115 client-owned dogs evaluated because of various health problems requiring urinalysis or to screen for proteinuria in an area endemic for leishmaniasis.230 paired urine samples, 1 collected by cystocentesis and 1 by free catch, were collected from the 115 dogs. The UPC ratio was determined in paired urine samples (n = 162) from 81 dogs with no indication of active inflammation according to urine sediment analysis. On the basis of the UPC ratio of urine sample collected by cystocentesis, dogs were classified as nonproteinuric (UPC ratio < 0.2), borderline proteinuric (UPC ratio of 0.2 to 0.5), or proteinuric (UPC ratio > 0.5), according to the International Renal Interest Society (IRIS).The correlation between UPC ratio in urine samples collected by cystocentesis and by free catch was strong (r(2) = 0.90); 75 of 81 (92.6\%) dogs had UPC ratios from both urine samples that resulted in classification in the same IRIS substage with a kappa coefficient of 0.83.The UPC ratio in dogs was minimally affected in urine samples collected by free catch, thus allowing correct grading of proteinuria with this method. The high reliability of the UPC ratio in free-catch urine samples coupled with the ease of collection should increase the use of this value for assessment of proteinuria.