New Cutoffs for the Biochemical Diagnosis of Adrenal Insufficiency after ACTH Stimulation using Specific Cortisol Assays.

Abstract

CONTEXT:

The normal cortisol response 30 or 60 minutes after cosyntropin (ACTH[1-24]) is considered to be ≥18 μg/dL (500 nmol/L). This threshold is based on older serum cortisol assays. Specific monoclonal antibody immunoassays or LC-MS/MS may have lower thresholds for a normal response.

OBJECTIVE:

To calculate serum cortisol cutoff values for adrenocorticotropic hormone (ACTH) stimulation testing with newer specific cortisol assays.

METHODS:

Retrospective analysis of ACTH stimulation tests performed in ambulatory and hospitalized patients suspected of adrenal insufficiency (AI). Serum samples were assayed for cortisol in parallel using Elecsys I and Elecsys II immunoassays, and when volume was available, by Access immunoassay and LC-MS/MS.

RESULTS:

A total of 110 patients were evaluated. Using 18 μg/dL as the cortisol cutoff after ACTH stimulation, 14.5%, 29%, 22.4%, and 32% of patients had a biochemical diagnosis of AI using the Elecsys I, Elecsys II, Access, and LC-MS/MS assays, respectively. Deming regressions of serum cortisol were used to calculate new cortisol cutoffs based on the Elecsys I cutoff of 18 μg/dL. For 30-minute values, new cutoffs were 14.6 μg/dL for Elecsys II, 14.8 μg/dL for Access, and 14.5 μg/dL for LC-MS/MS. Baseline cortisol <2 μg/dL was predictive of subnormal stimulated cortisol values.

CONCLUSION:

To reduce false positive ACTH stimulation testing, we recommend a new serum cortisol cutoff of 14 to 15 μg/dL depending on the assay used (instead of the historical value of 18 μg/dL with older polyclonal antibody assays). Clinicians should be aware of the new cutoffs for the assays available to them when evaluating patients for AI.

• Authors: Bradley R Javorsky, Hershel Raff, Ty B Carroll, Alicia Algeciras-Schimnich, Ravinder Jit Singh, Jessica M Colón-Franco, James W Findling
• Journal: Journal of the Endocrine Society (J Endocr Soc) Vol. 5 Issue 4 Pg. bvab022 (Apr 01 2021) ISSN: 2472-1972 [Electronic] United States
• PMID: 33768189 (Publication Type: Journal Article)
• Copyright: © The Author(s) 2021. Published by Oxford University Press on behalf of the Endocrine Society.