Desmopressin Stimulation Test: Worth to Use in Clinical Practise?

Differential diagnosis of Cushing’s disease (CD) is still problematic. Desmopressin testing may be an alternative tool to differentiate patients with CD. We assessed the effects of desmopressin (DDAVP) on the release of ACTH and cortisol (F) when given to patients with Cushing’s syndrome (CS) of varied aetiologies and normal individuals (NI). Fourteen patients with CD formed group I, nine patients with adrenal CS and three patients with ectopic ACTH secretion formed group II and fourteen NI formed group III. Net increments (∆) and percent increments (∆%) in F and ACTH were calculated following 10 µg DDAVP. ∆F% over 20% and in ∆ACTH% over 50% were accepted as positive response to the test. ∆F and ∆F% were significantly higher in group I when compared to group II and III (p<0.01 and p<0.001, respectively). ∆ACTH and ∆ACTH% were also significantly higher in group I comparing with group II and III (p<0.001 and p<0.001, respectively). Positive response was observed in 10/14 (71.42%) of patients in group I, in 3/12 (25%) of patients in group II and in 3/14 (21.42%) of healthy subjects in group III. Interestingly 2/3 of patients with ectopic ACTH secretion showed positive response. The sensitivity of the test was 71.42% and the specificity was 76.92%. The diagnostic accuracy was found to be 75%. These data provide some evidence that DDAVP testing is not an enough diagnostic tool for differential diagnosis of CD, since hyperresponsive patients to the peptide are not so uncommon in ectopic ACTH dependent CS.