Cortisol assays across the physiologic spectrum: access immunoassay compared with LC-MS/MS.

Area of Science:

• Endocrinology
• Clinical Chemistry
• Assay Development

Background:

• Cortisol immunoassays are widely used for adrenal function testing.
• Previous studies have not comprehensively validated immunoassay performance against LC-MS/MS across the full spectrum of cortisol production.

Purpose of the Study:

• To compare the performance of the Access Cortisol immunoassay with LC-MS/MS for serum cortisol measurement.
• To assess immunoassay accuracy across morning, post-dexamethasone suppression, and post-cosyntropin stimulation conditions.

Main Methods:

• A cross-sectional study involving 97 adults without adrenal disease.
• Serum cortisol was measured using the Access Cortisol immunoassay and LC-MS/MS at three time points.
• Analysis included correlation and concordance assessments using common clinical cutoffs.

Main Results:

• The Access Cortisol immunoassay showed good correlation with LC-MS/MS across the physiologic spectrum.
• Agreement was closer at lower cortisol levels (post-dexamethasone suppression) than at higher levels (post-cosyntropin stimulation).
• High concordance (Cohen's κ > 0.89) was observed using standard interpretative cutoffs for all conditions.

Conclusions:

• The Access Cortisol immunoassay provides reliable cortisol measurements comparable to LC-MS/MS.
• Clinicians can be confident in using this immunoassay for evaluating adrenal function across varying cortisol levels.