AJVR • Vol 79 • No. 5 • May 2018 525 T he use of dry reagent strips (dipsticks) is an es- sential component of a complete urinalysis, in addition to determination of physical properties and analysis of urinary sediment. Dipsticks are easy to use and provide immediate, semiquantitative results. Interpretation of the results provides information re- garding urinary tract health as well as systemic health of an animal. Most commercially available urine dipsticks in- clude test pads for bilirubin, blood, glucose, ketones, leukocytes, nitrites, pH, protein, urobilinogen, and urine SG. Of these tests, results for leukocytes are un- reliable, 1–4 and urobilinogen and nitrites are of little clinical relevance in dogs and cats. Dipstick methods for approximation of SG of dogs and cats are consid- ered unsatisfactory. 3,4 Effect of blood contamination on results of dipstick evaluation and urine protein-to-urine creatinine ratio for urine samples from dogs and cats Aida I. Vientós-Plotts DVM Ellen N. Behrend VMD, PhD Elizabeth G. Welles DVM, PhD Dennis J. Chew DVM Philippe R. Gaillard PhD Jessica N. Busler PhD Hollie P. Lee Received May 12, 2017. Accepted August 31, 2017. From the Departments of Clinical Sciences (Vientós-Plotts, Behrend, Lee) and Pathobiology (Welles), College of Veterinary Medicine, and the Department of Mathematics and Statistics, College of Sciences and Mathematics (Gaillard, Busler), Auburn University, Auburn, AL 36849; and the Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210 (Chew). Dr. Vientós-Plotts’ present address is Department of Veterinary Medicine and Surgery, College of Veterinary Medicine, University of Mis- souri, Columbia, MO 65211. Address correspondence to Dr. Behrend (behreen@ auburn.edu). OBJECTIVE To evaluate effects of blood contamination on dipstick results, specifc gravity (SG), and urine protein-to-urine creatinine ratio (UPCR) for urine samples from dogs and cats. SAMPLE Urine samples collected from 279 dogs and 120 cats. PROCEDURES Urine pools were made for each species (dogs [n = 60] and cats [30]). Blood was added to an aliquot of a pool, and serial dilutions were prepared with the remaining urine. Color and dipstick variables were recorded, and SG and UPCR were measured. For cats, 1 set of pools was used; for dogs, 2 sets were used. Comparisons were made between undiluted urine and spiked urine samples for individual colors. Repeated-measures ANOVA on ranks was used to compare dipstick scores and UPCR results; χ 2 tests were used to compare proteinuria categorizations (nonproteinuric, borderline, or proteinuric). RESULTS Any blood in the urine resulted in signifcantly increased dipstick scores for blood. In both species, scores for bilirubin and ketones, pH, and SG were affected by visible blood contamination. No signifcant difference for the dipstick protein reagent results was evident until a sample was visibly hema- turic. The UPCR was signifcantly increased in dark yellow samples of both species. Proteinuria categorizations differed signifcantly between undiluted urine and urine of all colors, except light yellow. CONCLUSIONS AND CLINICAL RELEVANCE Any degree of blood contamination affected results of dipstick analysis. Effects depended on urine color and the variable measured. Microscopic blood contamination may affect the UPCR; thus, blood contamination may be a differential diagnosis for proteinuria in yellow urine samples. ( Am J Vet Res 2018;79:525–531) Hematuria may be present in patients with clini- cal signs related to the urinary tract. In addition, blood can be introduced during cystocentesis. The presence of blood can change urine color, which potentially affects the color of the dipstick reagent pads and the apparent results (ie, colorimetric inter- ference as perceived visually). Even when hematuria is not visible, the presence of microscopic amounts of blood could alter a dipstick pad reaction by changing the urine composition. To our knowledge, the effect of blood contamination on dipstick results for urine samples from dogs and cats has not been evaluated. Blood contamination could also affect SG measure- ment by use of a refractometer, but to our knowledge, such interference has not been assessed. Evaluation of proteinuria is of particular inter- est 5 because it is associated with both systemic dis- ease and death attributable to renal failure in dogs and cats. 6–9 The UPCR is the best assessment of clini- cally important proteinuria. In addition to causing a ABBREVIATIONS SG Specifc gravity UPCR Urine protein-to-urine creatinine ratio