Relationships among urinary protein-to-creatinine ratio, urine specific gravity, and bacteriuria in canine urine samples.

Background Proteinuria is a marker of chronic kidney disease in dogs and a risk factor for increased morbidity and death. Predictive models using the results of readily available screening tests could foster early recognition. Objective To determine whether urine specific gravity (USG) and semiquantitative category of dipstick protein can be used to predict urinary protein-to-creatinine ratio (UP : C) and to examine the effect of urine culture results on UP : C in dogs. Animals Three hundred ninety-four dogs (482 visits) presented to a university Community Practice Clinic or Veterinary Teaching Hospital between January 2011 and November 2015. Methods Retrospective study. Medical records were searched to identify dogs for which urinalysis, UP : C measurement, and urine culture testing were performed during a single hospital visit. Urine specific gravity, UP : C, dipstick protein concentration, and findings of urine sediment analysis and urine culture were recorded. Regression or Spearman correlation analysis was used to test for relationships between UP : C and USG within dipstick categories and between UP : C and bacterial colony-forming units per milliliter, respectively. Cohen's kappa test was used to evaluate agreement between urine culture and UP : C testing. Results There were significant (P < .05) weak negative correlations (R-2 range, 0.14-0.37) between UP : C and USG for all nonnegative urine protein dipstick categories. The presence of a positive urine culture did not agree with the presence of abnormal UP : C (kappa = -0.06). Conclusions and Clinical Importance Within dipstick protein categories, UP : C cannot be accurately predicted from USG. Repeating UP : C measurement after resolution of urinary tract infection is advisable.