title: Measurement of proteinuria in dogs: analytic and diagnostic differences using 2 laboratory methods.
abstract: BACKGROUND
  Urinary protein-to-creatinine (UPC) ratio is an early diagnostic and prognostic marker of renal disease in dogs. Pyrogallol red molybdate (PRM) and Coomassie brilliant blue (CBB) are the most popular dye-binding assays for measurement of proteinuria. Published guidelines recommend strict cut-off points to substage patients with chronic renal diseases, irrespective of the assay applied. However, analytic variability and method-dependent differences could affect substaging of patients.
  
  
  OBJECTIVE
  The aims of this study were to analytically validate the CBB assay to evaluate possible method-dependent differences with PRM in urinary protein (UP) determination, and to assess the influence of such differences in substaging according to the International Renal Interest Society (IRIS).
  
  
  METHODS
  Urine was collected from healthy and proteinuric dogs. Intra-assay and inter-assay repeatability (imprecision), linearity under dilution (LUD), and spiking recovery (inaccuracy) were determined for the CBB assay. Split samples were measured with PRM and CBB, and agreement between methods and concordance in classification according to IRIS guidelines was determined.
  
  
  RESULTS
  The CBB assay was precise (< 10%) at all urine protein concentrations after excluding outliers from the intra-assay precision assay of high urine protein concentrations. Acceptable accuracy was demonstrated with both LUD and spiking recovery test. Both UP and UPC determined by CBB were significantly higher (P < .0001) than those obtained with PRM, and both a constant and proportional bias were present. Concordance of IRIS substaging was only moderate.
  
  
  CONCLUSIONS
  The CBB is precise and accurate, but the higher UPC obtained with CBB vs PRM may affect interpretation of the IRIS guidelines.
authors: Department of Veterinary Sciences and Public Health, University of Milan, Milan, Italy. gabriele.rossi@unimi.it.
authors: Gabriele
authors: G
authors: Rossi
authors: Veterinary Animal Hospital "Città di Pavia", Pavia, Italy.|Veterinary Laboratory "La Vallonea", Alessano (LE), Italy.
authors: Walter
authors: W
authors: Bertazzolo
authors: Department of Veterinary Sciences and Public Health, University of Milan, Milan, Italy.
authors: Monica
authors: M
authors: Binnella
authors: Department of Veterinary Sciences and Public Health, University of Milan, Milan, Italy.
authors: Paola
authors: P
authors: Scarpa
authors: Department of Veterinary Sciences and Public Health, University of Milan, Milan, Italy.
authors: Saverio
authors: http://orcid.org/0000-0001-7117-7987
authors: S
authors: Paltrinieri
mesh_terms: D000818:Animals; D004283:Dog Diseases / Q000175:diagnosis*; D004285:Dogs; D007674:Kidney Diseases / Q000175:diagnosis / Q000662:veterinary*; D011507:Proteinuria / Q000175:diagnosis / Q000662:veterinary*; D016482:Urinalysis
keywords: Analytic validation; Coomassie brilliant blue; International Renal Interest Society; pyrogallol red molybdate; urinary protein-to-creatinine ratio