Urinary cortisol-creatinine ratio in dogs with hypoadrenocorticism

Background Basal serum cortisol (BSC) >= 2 mu g/dL (>55 nmol/L) has high sensitivity but low specificity for hypoadrenocorticism (HA). Objective To determine whether the urinary corticoid:creatinine ratio (UCCR) can be used to differentiate dogs with HA from healthy dogs and those with diseases mimicking HA (DMHA). Animals Nineteen healthy dogs, 18 dogs with DMHA, and 10 dogs with HA. Methods Retrospective study. The UCCR was determined on urine samples from healthy dogs, dogs with DMHA, and dogs with HA. The diagnostic performance of the UCCR was assessed based on receiver operating characteristics (ROC) curves, calculating the area under the ROC curve. Results The UCCR was significantly lower in dogs with HA (0.65 x 10(-6); range, 0.33-1.22 x 10(-6)) as compared to healthy dogs (3.38 x 10(-6); range, 1.11-17.32 x 10(-6)) and those with DMHA (10.28 x 10(-6); range, 2.46-78.65 x 10(-6)) (P < .0001). There was no overlap between dogs with HA and dogs with DMHA. In contrast, 1 healthy dog had a UCCR value in the range of dogs with HA. The area under the ROC curve was 0.99. A UCCR cut-off value of <1.4 yielded 100% sensitivity and 97.3% specificity in diagnosing HA. Conclusions and Clinical Importance The UCCR seems to be a valuable and reliable screening test for HA in dogs. The greatest advantage of this test is the need for only a single urine sample.