The high-dose dexamethasone suppression test is used in dogs diagnosed with Cushings to differentiate pituitary-dependent from adrenal-dependent disease.
Plain (red top) or Gel tube. Minimum volume 2 ml serum.
- Collect a resting serum sample (red top tube) at zero hours and label it “0 hour”
- Allow tube to clot. If possible separate the serum from the red cells by centrifugation. If a plain tube has been used for the assay, centrifuge and transfer the serum from the collection tube into a plain (red top tube). Store at 4 degrees.
- Inject dexamethasone sodium phosphate intravenously at a dose rate of 0.1 mg/kg of body weight.
- Collect a serum sample at 3 hours post injection, label as “3hr”. Follow separation instructions as above.
- Collect a serum sample at 8 hours post injection, label as “8hr”. Follow separation instructions as above.
- Submit all samples to the laboratory ensuring the tubes are correctly labelled, and request serum cortisol testing.
- Diabetic patients - Give half the regular morning dose of insulin and monitor blood glucose every 1 to 2 hours throughout the procedure.
- Patients should be maintained in a stress-free environment for the duration of the test. Avoid testing in sick or stressed animals.