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Low-dose dexamethasone suppression test
Synonym(s): LDDST
Overview
- Administration of exogenous glucocorticoid (dexamethasone) suppresses hypothalamic-pituitary axis
. - Natural cortisol levels are suppressed for 78 h in normal animal.
- Dogs with hyperadrenocorticism show breakthrough of suppression by 8 h.
Uses
In combination
- In conjunction with clinical suspicion - diagnosis of hyperadrenocorticism (HAC) Hyperadrenocorticism.
- Potentially able to differentiate between adrenal dependent HAC and pituitary dependent HAC.
Other points
- The LDDST lacks specificity so its use is only recommended when there is strong clinical evidence to support a diagnosis of hyperadrenocorticism and other differentials for PUPD have been excluded. False positives are common with non-adrenal illness or stress.
- Takes 8 h to complete.
- Does not provide pre-treatment information for monitoring trilostane Trilostane therapy.
- Cannot be used to diagnose hypoadrenocorticism Hypoadrenocorticism, iatrogenic hyperadrenocorticism or to monitor treatment of hyperadrenocorticism.
Sampling
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Tests
Availability
- Widely available at commercial laboratories.
Validity
Sensitivity
- More reliable than ACTH stimulation test ACTH assay in confirming hyperadrenocorticism).
- Overall sensitivity around 96.6%.
- Lack of suppression at both 4 h and 8 h has the highest positive predictive vaule.
- Escape or inverse patterns are associated with a lower positive predictive value.
Specificity
- Specificity 67.2%.
- More affected by non-adrenal disease than the ACTH stimulation test.
- Specificity is poor in dogs with non-adrenal illness or concurrent diseases (especially diabetes melllitus Diabetes mellitus).
Do not perform adrenal function tests in ill animals. - Only perform LDDST in animals where there is a strong indication to do so.
Technician extrinsic limitations
- Must be able to give intravenous injection and collect samples without stressing animal.
Result Data
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Further Reading
Publications
Refereed papers
- Recent references from VetMedResource and PubMed.
- Bannaim M, Shiel R E, Forde C & Mooney C T (2018) Evaluation of individual low dose dexamethasone test patterns in naturally occurring hyperadrenocorticism in dogs. JVIM 32(3), 967-977 PubMed.
- Vaessen M M A R, Kooistra H S, Mol J A & Rijnberk A (2004) Urinary corticoid:creatinine ratios in healthy pet dogs after oral low-dose dexamethasone suppression tests. Vet Rec 155, 518-521.
- Feldman E C, Nelson R W, Feldman M S (1996) Use of low- and high-dose dexamethasone suppression tests for distinguishing PDH from ADH in dogs. JAVMA 209, 772-775 PubMed.
- Chauvet A E, Feldman E C, Kass P H (1995) Effects of phenobarbital administration on results of serum biochemical analyses and adrenocortical function tests in epileptic dogs. JAVMA 207, 1305-1307.
- Kaplan A J, Peterson M E, Kemppainen R J (1995) Effects of disease on the results of diagnostic tests for use in detecting hyperadrenocorticism in dogs. JAVMA 207, 445-451.
Other sources of information
- Most commercial laboratories will provide information on test and interpretation of data.