Preferred screening test for Cushing’s syndrome screening
Background: In our practice 24 hours urine collection for free cortisol (24Hr UFC) and overnight dexamethasone suppression test (ONDST) are initial investigations to screen patients for hyper-cortisolism. I audited our practice to find our clinicians’ and patients’ choice of first screening investigation for hyper-cortisolism. Method & material: Electronic and paper medical records of patients who underwent 24Hr UFC and/or ONDST at our hospital over previous consecutive twenty four months were examined. 62 such patients were identified but 12 patients were excluded from analysis. We tried to contact 30 patients over consecutive 48 hours over the phone who underwent both 24Hr UFC and ONDST. We managed to contact 18 patients and asked them two study questions. Data & results: 33 (66%) patients were female and 17 (33%) were male. 20 (40%) had 24Hr UFC alone and 30 (60%) patients had both. In total 80 such investigations completed 30 being ONDST and 50 24hr UFC. 53 (66%) of the investigations were requested by Endocrinologists, 21 (26%) by Hospital General Physicians and 6 (8%) by General practitioners (GP). For UFC 10 (20%) were true positive, 31 (62%) were false positive, 6 (12%) were true negative and 0% false negative. 3 (6%) 24Hr UFC samples were not collected properly and were not processed for results. Out of the total false positives (31 patients), 6 (19.3%) cases were of alcohol excess, 4 (13%) of dépression, 3 (9.7%) of inhaled steroids and 1 (3.2%) of sleep apnea. For the ONDST 7 (23.3%) true positive, 4 (13.3%) false positive 19 (63.4%) true negative and 0% false negative. All 18 patients contacted over the phone answered both questions. 16 preferred ONDST over 24Hr UFC, 1 patient had no preference and 1 patient preferred 24Hr UFC over ONDST. Conclusion: Patients overwhelmingly preferred ONDST as first screening test in contrast to physician’s choice of 24Hr UFC.