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Dexamethasone Suppression Test, High-Dose

Item Value
Approval req'd? No
Available Stat? No
Test code
Test group Dexamethasone Suppression Test
Container type
Sample type see Cortisol
Normal range See Additional Information
Additional information For Differential Diagnosis of Cushing's Syndrome.

Rapid Test (based on Tyrrell JB et al. Ann Intern Med 1986;104:180.: Obtain a baseline serum cortisol at 0700-0800 hours. Administer 8.0 mg po dexamethasone that evening at 2300 hours and obtain another serum cortisol at 0700-0800 hours the following morning. Interpretation: A positive response (suppressibility) is a reduction of the post-dexamethasone serum cortisol to <=50% of the baseline cortisol level (sensitivity 89%, CI 80-94%; specificity 100%, CI 84-100%).

Standard Test (based on Liddle GW. J Clin Endocrinol Metab 1960;20:1539): Obtain a baseline serum cortisol at 0700-0800 hours and a 24 hour urine collection of urine for 17-OH corticosteroids beginning at the same time. On the following day administer 2.0 mg po dexamethasone q6h for 8 doses. Repeat the 24 hour urine 17-OHS collection during day 2 of dexamethasone administration and repeat the plasma cortisol at 0700-0800 hours on the morning after the last steroid dose. Interpretation: A positive response (suppressibility) is a reduction in both assays to <=50% of baseline values (sensitivity 92%, CI 82-97%; specificity 94%, CI 85-97%).

Significance: A positive response generally indicates an ACTH-producing pituitary tumor, rather than an ectopic (primarily thoracic) ACTH-producing tumoror an adrenal source.
Last Updated 10/15/2008 9:50:01 AM
Entry Number 300
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