High-Dose Dexamethasone Suppression Test (Canine)

Indications

Differentiation between pituitary and adrenal forms of hyperadrenocorticism (Cushing's disease) in dogs already diagnosed with hyperadrenocorticism via ACTH stimulation or low-dose dexamethasone suppression (LDDS) testing.
Not indicated for the initial diagnosis of hyperadrenocorticism.

Notes

High-dose dexamethasone suppression (HDDS) is indicated for use in dogs already diagnosed as having hyperadrenocorticism where no suppression is seen on the LDDS at 4 and 8 hours.
Suppression during an HDDS test, in dogs already diagnosed as having hyperadrenocorticism, is consistent with pituitary-dependent hyperadrenocorticism. Failure to suppress could occur with both pituitary-dependent or adrenal-dependent hyperadrenocorticism and further diagnostics would be necessary to differentiate (e.g. abdominal ultrasound).

Protocol

Collect a baseline blood sample (1-2 ml in a plain/gel tube).
Inject 0.1 mg/kg of dexamethasone intravenously, via IV catheter.
Collect the second blood sample (1-2 ml in a plain/gel tube) 4 hrs post-injection.
Collect the third blood sample (1-2 ml in a plain/gel tube) 8 hrs post-injection.
Ensure the samples have clotted and centrifuge the samples 30-120 minutes after collection.
For samples collected in plain tubes, please separate the serum into another plain tube (this step is not necessary for samples collected in gel tubes).
Please label all tubes with the patient's name and the time of sampling.
Please include the patient history, including drug history, on the request form.
Submit the separated serum samples and the request form to the reference laboratory (Test code DEXH).
Cortisol will be measured in all three samples.

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Indications

Notes

Protocol

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