Updated April 13, 2021
Cushings disease is one of the most common diseases of dogs. The problem can be in getting an accurate diagnosis. Here I share some recent research that helps you know whether it could be the cause of illness in your dog.
This is important because no test is every 100% accurate.
Cushings Disease Tests
Cushing’s Syndrome is a disease of excessive cortisol production. The ACTH Stimulation Test (AST) measures how high the cortisol goes after an injection of ACTH. The Low Dose Dexamethasone Suppression Test (LDDST) measures how low the cortisol goes after a dexamethasone dose.
Neither test is especially accurate. ASTs are believed to have a false positive rate of 5-10% and a false negative rate of 20%. The LDDST is much the same in reverse. Therefore, if you screen the general dog population, where Cushing’s disease sits at around 0.3%, most of the positive results will be false positives.
If this seems crazy, check out this longer post on false positives.
This is where an online tool can help.
A Diagnostic Tool For Cushings
Recent analysis of large numbers of dogs with and without Cushing’s disease has shown that there are certain features that can be used to make a prediction. This is important for four reasons:
- A high probability suggests that testing, though expensive, is worth doing
- A low probability with a positive test should make you suspicious of a false positive
- A high probability with a negative test should make you suspicious of a false negative
- A probability that matches the test result helps improve confidence in starting treatment
To use this tool, just enter a score for each line, then subtract or add each number to get the actual score. It will work better if you’ve already had some basic blood and urine tests done.
|Current age (years)||<7||0|
|West Highland white terrier||−3|
|Other breed or crossbreed||0|
|Drinking a lot||Yes||2|
|Urine concentration||Dilute (USG≤ 1.020)||0|
|Not dilute (USG> 1.020)||−2|
|ALKP liver enzyme||Elevated||0|
|(blood test)||Not elevated||−3|
Now look up the percent chance that your dog has Cushing’s Disease in the following table.
|Points total||Cushings Prediction|
Hopefully the answer will help you decide what to do next, especially if your funds aren’t limitless. Remember: these are just probabilities, and must be confirmed with specific testing by your veterinarian.
Now Read: Treatment Of Cushing’s Disease
Schofield, I, Brodbelt, DC, Niessen, SJM, et al. Development and internal validation of a prediction tool to aid the diagnosis of Cushing’s syndrome in dogs attending primary‐care practice. J Vet Intern Med. 2020; 34: 2306– 2318. https://doi.org/10.1111/jvim.15851
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By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. These articles are from a series regularly posted on email and Twitter. Subscribe via email here to never miss a story!