Comparison of Single, Averaged, and Pooled Urine Protein:Creatinine Ratios in Proteinuric Dogs Undergoing Medical Treatment.

Background: Monitoring urine protein:creatinine ratios (UPC) in dogs with protein-losing nephropathy (PLN) is challenging because of day-to-day variation in UPC results.
Hypothesis/objectives: Determine whether single, averaged, or pooled samples from PLN dogs receiving medical treatment yield comparable UPCs, regardless of degree of proteinuria.
Animals: Twenty-five client-owned PLN dogs receiving medical treatment.
Methods: UPC ratios were prospectively measured in each dog utilizing 3 methods: single in-hospital sample (day 3), average sample (days 1-3), and pooled sample (equal pooling of urine from days 1-3). Bland-Altman analysis was performed to evaluate agreement between methods for all dogs, as well as in subgroups of dogs (UPC ≤4 or UPC >4).
Results: For all dogs, Bland-Altman log-transformed 95% limits of agreement were -0.07-0.18 (single versus pooled UPC), -0.06-0.16 (single versus average UPC), and -0.06-0.04 (pooled versus average UPC). For dogs with UPC ≤4, Bland-Altman 95% limits of agreement were -0.42-0.82 (single versus pooled UPC), -0.38-0.76 (single versus average UPC), and -0.27-0.25 (pooled versus average UPC). For dogs with UPC >4, Bland-Altman 95% limits of agreement were -0.17-2.4 (single versus pooled UPC), -0.40-2.2 (single versus average UPC), and -0.85-0.43 (pooled versus average UPC).
Conclusions and Clinical Importance: UPC ratios from all methods were comparable in PLN dogs receiving medical treatment. In PLN dogs with UPC >4, more variability between methods exists likely because of higher in-hospital results, but whether this finding is clinically relevant is unknown.
(Copyright © 2017 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)