Corticotrophin-releasing hormone and desmopressin tests in the differential diagnosis between Cushing's disease and pseudo-Cushing state: a comparative study.

BACKGROUND: We recently proposed a new and effective way of interpreting human corticotrophin-releasing hormone (hCRH) and desmopressin (DDAVP) tests, for the differential diagnosis between Cushing's disease (CD) and pseudo-Cushing state (PC), based on the simultaneous analysis of ACTH and cortisol. OBJECTIVE: The study had the aims of comparing the diagnostic performance of the two tests and determining whether carrying out both tests was more beneficial than carrying out only one. PATIENTS AND MEASUREMENTS: We studied 30 CD, 18 PC and 12 control (CT) subjects: in these patients, hCRH test, DDAVP test, 24-h urinary free cortisol, serum cortisol after overnight 1-mg dexamethasone suppression test and serum cortisol circadian rhythm were performed. RESULTS: The hCRH test and the DDAVP test showed an identical and excellent diagnostic performance (sensitivity 96·6% and specificity 100% for both tests); moreover, the hCRH and DDAVP tests showed almost perfect diagnostic agreement (κ = 0·93; P < 0·05) with a significantly higher number of concordant diagnoses (58 cases of 60) than those resulting from all other possible combinations among the studied tests. Interestingly, there were no subjects in whom both hCRH and DDAVP tests gave a simultaneous misdiagnosis. CONCLUSIONS: Our study indicates that the hCRH and DDAVP tests have similar diagnostic performance and present excellent agreement, without giving simultaneous misdiagnosis in any subject. Because of these characteristics, the use of both tests offers the physician a valuable tool for those cases of hypercortisolism which are difficult to interpret.