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Evaluation of endocrine tests. B: screening for hypercortisolism
F Holleman1, E Endert, M F Prummel
1Department of Endocrinology and Metabolism, Academic Medical Centre, Amsterdam, the Netherlands. f.holleman@amc.uva.nl
The Netherlands Journal of Medicine
|October 26, 2005
Summary
New cut-off values for 24-hour urinary free cortisol and post-dexamethasone plasma cortisol aid in diagnosing Cushing's syndrome. These established thresholds improve diagnostic accuracy for patients with suspected hypercortisolism.
Area of Science:
- Endocrinology
- Clinical Diagnostics
Background:
- Reference values for 24-hour urinary free cortisol and dexamethasone suppression tests exist for healthy individuals.
- Specific cut-off values are needed for patients suspected of Cushing's syndrome.
Purpose of the Study:
- To establish diagnostic cut-off values for 24-hour urinary free cortisol and post-dexamethasone plasma cortisol in patients with suspected Cushing's syndrome.
- To evaluate the diagnostic performance of these tests using ROC curve analysis.
Main Methods:
- Prospective follow-up study of 144 patients with suspected Cushing's syndrome and 50 with adrenal incidentaloma.
- Measurement of 24-hour urinary free cortisol and post-dexamethasone plasma cortisol.
- Diagnosis confirmed by histopathology and long-term follow-up.
Main Results:
- Optimal cut-off values were determined: 180 nmol/24 hours for urinary free cortisol (sensitivity 94%, specificity 94%) and 95 nmol/l for post-dexamethasone plasma cortisol (sensitivity 100%, specificity 94%).
- Receiver operating characteristic (ROC) curve analysis showed high diagnostic accuracy (AUC 0.958 for urinary cortisol, 0.985 for plasma cortisol).
Conclusions:
- Established cut-off values for 24-hour free urinary cortisol (180 nmol/24 hours) and post-dexamethasone plasma cortisol (95 nmol/l) are effective for evaluating patients with suspected hypercortisolism.
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