Evaluation of the DDAVP test in the diagnosis of Cushing's Disease.

To analyse the performance of the desmopressin (DDAVP) test in the diagnosis of Cushing's disease (CD). This was a prospective cohort study of 124 patients with suspected hypercortisolism who were recruited from an outpatient endocrinology clinic and investigated for Cushing's syndrome (CS). The ACTH and cortisol responses to the DDAVP test were assessed to determine patient diagnosis and test the procedure's diagnostic accuracy. A total of 68 patients had CD, while 56 had suspected CS. According to ROC analysis, an ACTH peak of 71·8 pg/ml (15·8 pmol/l) following DDAVP administration was able to diagnose CD with a specificity of 94·6% and a sensitivity of 90·8%, a negative predictive value (NPV) of 89·9% and a positive predictive value (PPV) of 95·3%. An absolute ACTH increment ≥37 pg/ml (8·1 pmol/l) over baseline had a sensitivity of 88·0%, specificity of 96·4%, NPV of 87·0% and PPV of 95·3% in diagnosing CD. Only 2 of 56 cases without CD had an absolute ACTH increment ≥37 pg/ml (8·1 pmol/l) over baseline. The DDAVP test was superior to other clinical instruments in diagnosing CS. The DDAVP test could be a useful additional tool to diagnose CD in patients with suspected CS.