ASSESSMENT OF THE UTILITY OF THE HIGH-DOSE DEXAMETHASONE SUPPRESSION TEST IN CONFIRMING THE DIAGNOSIS OF CUSHING DISEASE

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Abstract

Objective:

To determine the utility of high-dose dexamethasone suppression (HDDS) tests to confirm the diagnosis of Cushing disease (CD).

Methods:

In this retrospective study, we reviewed medical records of patients who underwent either the overnight 8-mg HDDS test or the 2-day 2-mg HDDS test every 6 hours. The percentage suppression of morning serum cortisol and the percentage suppression of 24-hour urine free cortisol (UFC) were calculated.

Results:

Of 141 patients with proven CD who underwent HDDS tests, 77 (55%) underwent the overnight 8-mg HDDS test and 64 (45%) underwent the 2-day 2-mg HDDS test every 6 hours. With the overnight 8-mg HDDS test, 73 of 77 patients (95%) had greater than 50% suppression and 48 of 77 patients (62%) had greater than 80% suppression of the morning serum cortisol in comparison with the baseline value. With the 2-day 2-mg HDDS test, only 41 of 64 patients (64%) had greater than 90% suppression of 24-hour UFC.

Conclusion:

We conclude that the overnight 8-mg HDDS test accurately confirmed the diagnosis of CD with a high sensitivity of 95% with use of a criterion of greater than 50% suppression; in contrast, the sensitivity was only 62% with use of a more precise cutoff of greater than 80% suppression. The 2-day 2-mg HDDS test with a criterion of greater than 90% suppression of 24-hour UFC had a sensitivity of 64%. These results confirm the limited precision of the HDDS tests. (Endocr Pract. 2012;18:152-157)

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