Affiliation:
1. Department of Endocrinology and Metabolism All India Institute of Medical Sciences New Delhi India
2. Department of Biostatistics All India Institute of Medical Sciences New Delhi India
Abstract
AbstractContextLate‐night salivary cortisol (LNSC) is a simple and reliable screening test for Cushing syndrome (CS). With improved analytical performance of the current second‐generation electrochemiluminescence immunoassay (ECLIA; Elecsys Cortisol‐II; Roche Diagnostics), there is a need to revisit the LNSC cut‐offs, especially in a South‐Asian population.ObjectiveTo derive LNSC cut‐offs for diagnosis of CS using second‐generation ECLIA kits.DesignDiagnostic accuracy study.MethodsWe prospectively recruited 155 controls aged 18–60 years, including, normal‐weight (body mass index [BMI] < 25 kg/m2 and no hypertension or diabetes [n = 53]) and overweight/obese (BMI 25–30 kg/m2 and hypertension and/or diabetes [n = 52] or BMI ≥ 30 kg/m2 with/without comorbidities [n = 50]) participants. All participants submitted LNSC samples collected at home; overweight/obese controls additionally underwent dexamethasone suppression test to exclude CS. We also reviewed records of adults with endogenous CS (cases, n = 92) and a valid LNSC result using the same method.ResultsThe 95th percentile for LNSC in controls was 6.76 nmol/L. The mean ± SD LNSC levels were 40.47 ± 49.63 nmol/L in cases and 3.37 ± 1.18 nmol/L in controls (p < 0.001). Receiver operating characteristic (ROC) analysis showed excellent diagnostic performance of LNSC for CS, with area under curves (AUCs) of 0.994 (cases vs. all controls) and 0.993 (cases vs. overweight/obese controls), respectively. The best diagnostic performance was achieved at cut‐offs ≥6.73 nmol/L (sensitivity: 97.8%, specificity: 94.8%) and ≥7.26 nmol/L (sensitivity: 97.8%, specificity: 95.1%), respectively.ConclusionsLNSC measured using second‐generation ECLIA demonstrated high diagnostic accuracy for CS. Based on this study, we propose a LNSC cutoff ≥6.73 nmol/L to diagnose CS.
Subject
Endocrinology, Diabetes and Metabolism,Endocrinology