Accuracy of Late-Night Salivary Cortisol in Evaluating Postoperative Remission and Recurrence in Cushing's Disease.

CONTEXT Late-night salivary cortisol (LNSC) is well-validated in the diagnosis of Cushing's disease (CD). The accuracy of LNSC during follow-up of patients undergoing transsphenoidal surgery (TSS) has not been fully characterized. OBJECTIVES We examined the accuracy of LNSC in establishing remission and identifying recurrence in postoperative patients with CD. DESIGN This is a retrospective study. PATIENTS Records of patients with CD who underwent TSS by a single neurosurgeon in our tertiary center (2005-2014) were analyzed (N = 224). Patients were selected for further investigation (n = 165) if there was at least one available LNSC test obtained after TSS (either within 3 months or during long-term follow-up). Extracted data included demographic and clinical characteristics, magnetic resonance imaging and laboratory data (morning serum cortisol, 24-hour urine free cortisol [UFC], LNSC) . MAIN OUTCOMES AND MEASURES Remission was defined as nadir morning serum cortisol less than 5 mcg/dl and nadir 24-hour UFC less than 23 mcg. Recurrence was considered definite if confirmed surgically or prompted radiotherapy. RESULTS Surgical remission occurred in 89% of 89 patients with available LNSC data. LNSC, obtained within 3 months of TSS, established remission with 94% sensitivity and 80% specificity at a cutpoint of 1.9 nmol/l (area under the curve [AUC] = 0.90). At a median follow-up of 53.5 months, LNSC established recurrence (75% sensitivity and 95% specificity) at a cutpoint of 7.4 nmol/l (AUC = 0.87), and 24-hour UFC established recurrence (68% sensitivity and 100% specificity) at a cutpoint of 1.6-fold above normal (AUC = 0.82). CONCLUSIONS LNSC may accurately establish remission after TSS and identify recurrence more accurately than 24-hour UFC during long-term follow-up.