Comparison of cystocentesis versus home sampling to determine urinary protein: Creatinine ratio and urine specific gravity in cats

BackgroundUrinalysis is necessary for the diagnostic evaluation of chronic kidney disease in cats. Performing cystocentesis is not always feasible, but data comparing urine obtained by cystocentesis in the clinic with voided samples collected at home are lacking in cats. ObjectivesTo compare urinary protein:creatinine ratio (UPC) and urine specific gravity (USG) and to detect clinically relevant changes in proteinuria substage or urine concentration between urine collected at home and in-clinic by cystocentesis in cats. AnimalsNinety-two healthy and diseased client-owned cats. MethodsProspective study. Owners collected voided urine at home and within 1 to 15 hours, cystocentesis was performed in the clinic. ResultsIn a subset of motivated owners, 55% succeeded in collecting urine at home. Overall, UPC was higher (mean & PLUSMN;SD difference = 0.09 & PLUSMN;0.22; P < .001) and USG was lower (mean & PLUSMN;SD difference = -0.006 & PLUSMN;0.009; P < .001) in cystocentesis samples than in voided urine. Substantial agreement existed between sampling methods for UPC (weighted k = 0.68) and USG (k = 0.64) categories. A different proteinuria substage (UPC < 0.2, 0.2-0.4, >0.4) was present in paired urine samples from 28% of cats. In 18% of cats, urine concentrating ability (USG < or & GE;1.035) differed between both samples. Conclusions and Clinical ImportanceHome sampling of urine is a valid alternative to cystocentesis in cats. However, because clinically relevant differences in UPC and USG were present in 28% and 18% of cats, respectively, by the same collection method for monitoring each cat is advised.