Evaluation of urine sulfated and nonsulfated bile acids as a diagnostic test for liver disease in dogs

Objective-To evaluate 3 methods for measuring urine bile acids (UBA) and compare their diagnostic performance with that of the serum bile acids (SBA) test and other routine screening tests in dogs with hepatic disorders. Design-Prospective study. Animals-1 5 healthy dogs, 102 dogs with hepatic disorders, and 9 dogs with clinical signs of hepatic disorders that were found to have nonhepatic disorders. Procedures-Blood and urine samples were collected from sick dogs and healthy dogs for serum biochemical analyses, and determination of concentrations of SBA and UBA. Urine samples were obtained from 15 healthy dogs to establish an upper cutoff value for UBA concentrations. The UBA were measured by use of a quantitative-linked enzymatic colorimetric method. Three analytical modifications were evaluated; 1 quantified only urine sulfated bile acids (USBA), 1 only urine nonsulfated bile acids (UNSBA), and 1 quantified both (USBA plus UNSBA). The UBA values were standardized with the urine creatinine concentration. Results-The UNSBA-to-creatinine ratio and USBA plus UNSBA-to-creatinine ratio tests had the best diagnostic performance of the UBA tests;, each had a substantially higher specificity, slightly higher positive predictive value, slightly lower negative predictive value, and lower sensitivity than the SBA test. These UBA-to-creatinine values were positively correlated with SBA values. The USBA-to-creatinine ratio had poor sensitivity, indicating a low rate of bile acid sulfation in dogs. Conclusions and Clinical Relevance-The UBA can be measured in dogs with sufficient repeatability and accuracy for clinical application. The UNSBA-to-creatinine ratio and USBA plus UNSBA-to-creatinine ratio identified dogs with hepatic disorders nearly as well as the SBA test.