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

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.We examined the accuracy of LNSC in establishing remission and identifying recurrence in postoperative patients with CD.This is a retrospective study.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) .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.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).LNSC may accurately establish remission after TSS and identify recurrence more accurately than 24-hour UFC during long-term follow-up.