Abstract

The diagnostic value of the 24-h integrated concentration (IC) test of cortisol (IC-24-F) was found to be superior to the value of both urinary 17OHCS and urinary free cortisol tests. The IC-24-F test is too cumbersome for widespread clinical use. The purpose of the present study was to evaluate the diagnostic value of an abbreviated and practical 6-h IC of cortisol (IC-6-F) test.

The IC of cortisol (IC-F) was measured in 68 normal subjects and 13 patients with surgically proven Cushing’s syndrome. A portable nonthrombogenic constant blood withdrawal system was used over a 24-h period. The IC-F was measured in plasma withdrawn during each ½-h period (IC-½-F).

The mean of 12 consecutive measurements of IC-½-F yielded the IC-6-F. The mean of all the IC-½-F collected over a 24-h period constituted the IC-24-F.

The IC-½-F of the patients and their IC-6-F from 0800-1400 h, 1400-2000 h, and 2000-0200 h overlapped the corresponding levels in the control subjects. There was no overlap between the IC-24-F and the IC-6-F (from 2000-0200 h) of the patients and the control subjects.

It was concluded that the diagnostic value of a 6-h IC-F testconducted during the afternoon and early part of the night is equal to the diagnostic value of the 24-h IC-F test. (J Clin Endocrinol Metab54: 1072,1982)

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