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Pseudo-Cushing syndrome caused by fenofibrate interference with urinary cortisol assayed by high-performance liquid
A Wayne Meikle1, James Findling, Mark M Kushnir
1Department of Medicine, University of Utah, Salt Lake City, Utah 84132, USA. wayne.meikle@hsc.utah.edu
The Journal of Clinical Endocrinology and Metabolism
|August 14, 2003
Summary
Fenofibrate medication can interfere with lab tests for Cushing syndrome, causing falsely high urinary free cortisol (UFC) levels. Using multiple mass transitions in HPLC-MS/MS testing ensures accurate UFC results in patients taking fenofibrate.
Area of Science:
- Endocrinology
- Clinical Chemistry
- Analytical Chemistry
Background:
- Urinary free cortisol (UFC) is a key biomarker for diagnosing Cushing syndrome.
- Accurate UFC measurement is crucial for differentiating between true disease and other conditions.
Observation:
- Two patients evaluated for Cushing syndrome presented with elevated UFC via HPLC but normal results via RIA and HPLC-MS/MS.
- Fenofibrate, a medication taken by the patients, was identified as a potential source of analytical interference.
Findings:
- Fenofibrate exhibits a chromatographic peak that overlaps with cortisol.
- Fenofibrate can produce a mass spectrometry/mass spectrometry (MS/MS) transition that interferes with cortisol quantitation.
- A validated HPLC-MS/MS method utilizing multiple mass transitions accurately quantified UFC even in the presence of fenofibrate.
Implications:
- Fenofibrate can lead to false-positive UFC results in HPLC and single-transition HPLC-MS/MS assays.
- Employing HPLC-MS/MS with multiple mass transitions is essential for reliable UFC measurement in patients taking fenofibrate.
- This finding highlights the importance of considering drug interference in diagnostic testing and assay validation.