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.