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Fecal Glucocorticoid Analysis: Non-invasive Adrenal Monitoring in Equids
Published on: April 25, 2016
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Dexamethasone measurement during low-dose suppression test for suspected hypercortisolism: threshold development with
F Ceccato1,2, C Artusi3, M Barbot4
1Endocrinology Unit, Department of Medicine DIMED, University-Hospital of Padova, Via Ospedale Civile, 105-35128, Padua, Italy. filippo.ceccato@unipd.it.
Journal of Endocrinological Investigation
|February 16, 2020
Summary
This study developed a dexamethasone threshold for the 1-mg dexamethasone suppression test (DST) to improve Cushing's Syndrome diagnosis. Measuring dexamethasone levels during DST enhances diagnostic accuracy by increasing specificity and reducing false positives.
Area of Science:
- Endocrinology
- Clinical Chemistry
- Diagnostic Medicine
Background:
- The 1-mg dexamethasone suppression test (DST) is crucial for diagnosing Cushing's Syndrome (CS).
- Diagnostic accuracy of DST can be limited by dexamethasone bioavailability.
- A validated dexamethasone threshold is needed to improve DST reliability.
Purpose of the Study:
- To develop and validate a dexamethasone threshold for the 1-mg DST.
- To assess the impact of dexamethasone levels on CS diagnostic accuracy.
- To enhance the specificity of cortisol measurements in the DST.
Main Methods:
- A cohort of 200 subjects (125 retrospective, 75 prospective validation) was studied.
- Serum dexamethasone, Late Night Salivary Cortisol (LNSC), and Urinary Free Cortisol (UFC) were measured using LC-MS/MS.
- A dexamethasone threshold was established using the lower 2.5th percentile in non-CS patients with specific cortisol levels.
Main Results:
- A dexamethasone threshold of 4.5 nmol/L was calculated.
- The 1-mg DST showed high sensitivity (100%) but moderate-low specificity (63%) for CS diagnosis.
- Incorporating dexamethasone levels reduced false positives and identified non-CS patients with inadequate dexamethasone absorption (6%).
Conclusions:
- Routine measurement of dexamethasone during 1-mg DST is feasible and validated.
- Dexamethasone levels are independent of patient clinical factors.
- Measuring dexamethasone during DST improves diagnostic specificity for Cushing's Syndrome.
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