The Urine Cortisol:Creatine Ratio test (UC:Cr) is a urine test which is used to diagnose and monitor Cushing's Disease.
Cushing's Disease is caused by an excess of the hormone cortisol in the blood. This increased blood cortisol causes a loss of cortisol in the urine, which can be measured by the Urine Cortisol:Creatine Ratio test.
Urine Cortisol - Creatine Ratio Test For Diagnosing Dog Cushing's Disease
A urine cortisol-creatinine ratio test is a screening test for Cushing's disease. Cushings, or hyperadrenocorticism, is when the adrenal glands produce excessive cortisol. This can cause elevated liver enzymes, increased water intake and urination, skin problems, and other complications.
A urine cortisol-creatinine ratio measures the amount of cortisol in the urine. It is easily done on a free-catch sample, so it is noninvasive and fairly inexpensive. If cortisol levels are low, Cushing's is ruled out and usually no further testing is required. However, if cortisol levels are high, you need to pursue additional testing. Cortisol in urine can be elevated due to stress or other disease processes so it does not automatically diagnose Cushing's disease. A normal urine cortisol: creatinine ratio (<13.5) rules out hyperadrenocorticism, but an abnormal urine cortisol: creatinine ratio (>13.5) may be associated with dogs with polyuria and polydipsia due to other causes (e.g., diabetes mellitus) and needs to be confirmed with either an ACTH stimulation test or dexamethasone screening test.
The diagnosis of Cushings is not always straightforward and sometimes multiple tests are required. The urine cortisol-creatinine ratio test is very sensitive (~100%), meaning it doesn't produce false negative results, and if the test is negative we can rule out HAC with confidence. On the other hand specificity of this test isn't very high (20-70%), meaning that positive results don't necessarily mean that the dog actually has HAC, as many other factors can influence the results.