[Evaluation of the 1 mg overnight dexamethasone suppression test in the diagnosis of the subclinical Cushing's syndrome in patients with Adrenal Incidentaloma].

Objective To evaluate efficacy of the 1 mg overnight dexamethasone suppression test (1 mg overnight DST) in the diagnosis of subclinical Cushing's syndrome, and to explore the best diagnostic cut-off value. Methods The clinical data of patients with adrenal incidentaloma in Chinese PLA General Hospital from 1995 to 2013 were gathered.The data of subclinical Cushing's syndrome(SCS) and non-functional adrenal adenoma (NFA) was retrospectively analyzed.The ROC curve was used to evaluate the efficacy of the 1 mg overnight DST and to explore the best cut-off value with high sensitivity and specificity. Results There were 447 patients with NFA (224 male and 223 female), and the mean age was 53±11 years old.49 patients were with SCS (19 male and 30 female), and the mean age was 47±12 years old.The area under the ROC of serum cortisol level after 1 mg overnight DST was 0.967 (95%CI: 0.942-0.993). The best cut-off value of serum cortisol after 1 mg overnight DST was 63.65 nmol/L , with a sensitivity of 100.0% and a specificity of 88.8% .The best cut-off value of the suppression ratio of serum cortisol was 85.64%, with a sensitivity of 83.3% and a specificity of 84.6%. Conclusions The best criterion for 1 mg overnight DST in the diagnosis of SCS was serum cortisol level , and the recommend cut-off point was 63.65 nmol/L, with both a higher sensitivity and specificity.The suppression ratio of serum cortisol after 1 mg overnight DST was also considered as a suitable criterion in the diagnosis of SCS. Key words: Subclinical Cushing's syndrome; Dexamethasone suppression test; Sensitivity; Specificity