Low-dose dexamethasone suppression test in Cats (Felis) | Vetlexicon
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Low-dose dexamethasone suppression test

ISSN 2398-2950


Synonym(s): LDDST

Overview

  • Administration of exogenous glucocorticoid (dexamethasone) suppresses hypothalamic-pituitary axis Endocrinology: hypopituitary adrenal axis - diagram .
  • Natural cortisol levels are suppressed for >8 hours in normal animal.
  • Animals with hyperadrenocorticism show breakthrough of suppression by 8 hours.
    Wider range of degree and duration of suppression in cats than dogs.

Uses

In combination

Other points

  • Affected by more variables than ACTH stimulation test ACTH stimulation test.
  • Takes 8 hours to complete.
  • High sensitivity but only moderate specificity for the diagnosis of hyperadrenocorticism.

Sampling

Source of test material

Quantity of test material

Either 1 ml serum/plasma per sample
Or 1-2 ml whole blood

Sample collection technique

  • Fast animal for 12 hours
  • Collect 1-2 ml venous blood into plain or heparinized tube.
  • Inject dexamethasone Dexamethasone 0.1 mg/kg IV (higher dose used compared to dogs because up to 10-20% of healthy cats do not suppress after 0.01 mg/kg).
  • Collect 1-2 ml of venous blood into plain or heparinized tube at 4 and 8 hours.
  • Separate plasma.
  • Perform cortisol assay on all samples.

Quality control

Precautions

  • Animal must remain unstressed throughout procedure.

Sample transport

  • Normal mail.

 

Tests

Availability

  • Widely available.

Technician extrinsic limitations

  • Must be able to give intravenous injection and collect samples without stressing animal.

Result Data

Normal (reference) values

  • [Plasma cortisol] = <50% of [basal cortisol] at 4 hours and failure to escape suppression by 8 hours (most cases).

Abnormal values

  • Hyperadrenocorticism: [cortisol] fails to suppress or escapes suppression by 8 hours.

Errors and artifacts

  • Stress: must be minimized.
  • No sedation possible.
  • Recent administration of exogenous glucocorticoids may suppress the hypothalamic-pituitary axis.
  • Recent administration of other glucocorticoids eg cortisol Hydrocortisone or prednisolone Prednisolone will cross-react in assay.

Further Reading

Publications

Refereed papers

  • Recent references from VetMedResource and PubMed.
  • Boland L A & Barrs V R (2017) Peculiarities of feline hyperadrenocorticism - Update on diagnosis and treatment. J Feline Med Surg 19, 933-947 PubMed.
  • Valentin S Y, Cortright C C, Nelson R W, Pressler B M, Rosenberg D, Moore G E & Scott-Moncrieff J C (2014) Clinical findings, diagnostic test results and treatment outcome in cats with spontaneous hyperadrenocorticism: 30 cases. JVIM 28 (2), 481-487 PubMed.
  • Medleau L, Cowan L A, Cornelius L M (1987) The effect of low dose intravenous dexamethasone administration. Res Vet Sci 42, 260-261.
  • Peterson M E, Graves T K (1987) The effects of low dosages of intravenous dexamethasone on serum cortisol concentrations in the normal cat. Am J Vet Res 48, 1719-1724.