Diagnostic pitfalls in Cushing\u27s disease impacting surgical remission rates; test thresholds and lessons learned in 105 patients.

CONTEXT: Confirming a diagnosis of Cushing\u27s disease (CD) remains challenging yet is critically important before recommending transsphenoidal surgery for adenoma resection. OBJECTIVE: To describe predictive performance of preoperative biochemical and imaging data relative to post-operative remission and clinical characteristics in patients with presumed CD. DESIGN, SETTING, PATIENTS, INTERVENTIONS: Patients (n=105; 86% female) who underwent surgery from 2007-2020 were classified into 3 groups: Group A (n=84) pathology-proven ACTH adenoma; Group B (n=6) pathology-unproven but with postoperative hypocortisolemia consistent with CD, and Group C (n=15) pathology-unproven, without postoperative hypocortisolemia. Group A+B were combined as Confirmed CD and Group C as Unconfirmed CD. MAIN OUTCOMES: Group A+B was compared to Group C regarding predictive performance of preoperative 24-hour urinary free cortisol (UFC), late night salivary cortisol (LNSC), 1mg dexamethasone suppression test (DST), plasma ACTH, and pituitary MRI. RESULTS: All groups had a similar clinical phenotype. Compared to Group C, Group A+B had higher mean UFC (p CONCLUSIONS: Use of strict biochemical thresholds may help avoid offering transsphenoidal surgery to presumed CD patients with equivocal data and improve surgical remission rates. Patients with Cushingoid phenotype but equivocal biochemical data warrant additional rigorous testing