Investigation for Paediatric Cushing's Syndrome Using Twenty-Four-Hour Urinary Free Cortisol Determination.

Objective: Paediatric Cushing's syndrome (CS) remains a challenge to diagnose and exclude. We assessed the accuracy of 24-hour urinary free cortisol (UFC) determination in children referred for suspected CS. Design: We conducted a retrospective study of paediatric patients referred to our centre with suspected CS between 1982 and 2014. Patients: Of 66 subjects (mean age 12.9 years; range 4.4-16.9), there were 47 cases of CS (29 males), which included Cushing's disease (CD; 39 patients, 25 males), primary pigmented nodular adrenocortical disease (8 patients, 4 males) and 19 'controls' (6 males) in whom the diagnosis of CS was excluded. Measurements: The subjects had between one and five 24-hour UFC collections analysed by radioimmunoassay, chemiluminescent immunoassay or liquid chromatographymass spectrometry. The data were normalised, corrected for body surface area (m(2)) and assessed using receiver operating characteristic analysis and an independent two-tailed t test. Results: The diagnostic accuracy of 24-hour UFC for CS was excellent (area under the curve 0.98, 95% CI 0.946-1.00, sensitivity 89%, specificity 100%). Conclusions: Twenty-four-hour UFC is a reliable and practical investigation with high diagnostic accuracy for paediatric CS. However, further investigations may be required if the UFC is normal but there is a high diagnostic suspicion of CS. (C) 2016 S. Karger AG, Basel