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

Abstract

Background Urinalysis 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. Objectives To 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. Animals Ninety‐two healthy and diseased client‐owned cats. Methods Prospective study. Owners collected voided urine at home and within 1 to 15 hours, cystocentesis was performed in the clinic. Results In a subset of motivated owners, 55% succeeded in collecting urine at home. Overall, UPC was higher (mean ±SD difference = 0.09 ±0.22; P < .001) and USG was lower (mean ±SD difference = −0.006 ±0.009; P < .001) in cystocentesis samples than in voided urine. Substantial agreement existed between sampling methods for UPC (weighted к = 0.68) and USG (к = 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 ≥1.035) differed between both samples. Conclusions and Clinical Importance Home 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.

Value of repeated health screening in 259 apparently healthy mature adult and senior cats followed for 2 years

“…Therefore, urine collected by voiding and cystocentesis are both appropriate for urinalysis in the context of health screening, as long as the same collection method is used when monitoring the UPC and USG of the same cat over time. 58 …”

Biological variation of urinary protein: Creatinine ratio and urine specific gravity in cats

“…When home sampling of urine is chosen, however, it is advisable to apply this sampling method at all time points used to identify persistence of borderline or overt proteinuria to be able to reliably compare serial UPC results in the same cat. 15 Because all urine samples for our current study were obtained by cystocentesis, caution is warranted when extrapolating biological variability data to voided urine.…”

“…The median (range) difference between both UPC values was 0.03 (range, 0-0.17) or 20% (range, 1%-112%) for these 15…”

“…[5][6][7][8][9] Recent studies have investigated preanalytical and analytical factors influencing these urinary variables, but information on biological variation of these biomarkers in cats is lacking. [10][11][12][13][14][15] This situation is in contrast to dogs, for which 1 study reported the RCV to be 35% at high UPC values (near 12) and 80% at low UPC values (near 0.5). 16 Previous articles stated that serial UPC values in cats need to differ by 90% to conclude that the level of proteinuria has increased, and that the goal of treatment in case of proteinuria is to achieve a > 90% decrease in UPC.…”