Evaluation of a urine dipstick test for confirmation or exclusion of proteinuria in dogs

Objective - To evaluate a urine dipstick test as a possible replacement for urine protein-to-creatinine (UPC) ratio for identifying proteinuria in dogs. Sample Population - 507 urine samples from adult dogs. Procedures - Urine dipstick, UPC ratio, specific gravity (USG), and sediment testing were performed on 507 samples. With UPC ratio as the reference criterion, diagnostic accuracy of the urine dipstick test was calculated for the entire data set and for urine samples grouped by USG (≤ 1.012 or > 1.012; < 1.030 or ≥ 1.030). A UPC ratio < 0.2 was used to indicate absence of proteinuria. Results - The sensitivity of the urine dipstick test for detection of proteinuria was > 90% when 0 mg of protein/dL (a 0+ result) was used to indicate a negative test result, and the specificity ranged from 40% to 60%, depending on the USG. Sensitivity decreased to a range of 56% to 81% when 30 mg of protein/dL (a 1 + result) was used as the cutoff, depending on the USG, but the specificity increased to > 90%.The likelihood of correctly identifying nonproteinuric dogs was low when the USG was ≤ 1.012, particularly when samples with a 1+ result were considered negative. Conclusions and Clinical Relevance - For dogs with a dipstick-test result of 1+ and USG ≤ 1.012, proteinuria should be assessed by use of the UPC ratio; dogs with a USG value > 1.012 are likely nonproteinuric. When used together, the urine dipstick test and USG measurement were reliable as a rapid alternative to UPC ratio determination in dogs in this study.