Newer Generation Immunoassays in Screening for Adrenal Insufficiency: Comparison of Baseline Morning Cortisol Levels...

Serum cortisol immunoassays with improved specificity for cortisol have prompted revisiting the definition of a normal response at 60-minute cosyntropin stimulation testing (CST-60) to ≥14 μg/dL. European and American Endocrine Societies define values of AM cortisol >10 μg/dL as adequate to rule out adrenal insufficiency (AI) in patients with long-term use of corticosteroids. We sought to compare AM cortisol levels with CST-60 in patients suspected of AI from various causes.

A retrospective review was performed from the electronic health record of a large midwestern hospital in patients who were evaluated for AI.

There were 95 patients (51women, age 58.8 ± 17.8 SD years) with 43 tests performed outpatient, 48 inpatient, and 4 ICU settings. The pretest diagnoses were adrenal abnormalities (n = 10), hyponatremia (n = 11), hypoglycemia (n = 9), fatigue (n = 19), hypotension (n = 35), pituitary abnormality (n = 7), and shock (n = 4). Binary logistic regression analyses and receiver operating curves compared AM cortisol as predictors of a normal CST-60 ≥ 14.6 μg/dL and to the previous criteria of a CST-60 ≥18.0 μg/dL. Receiver operating curves showed that an AM cortisol of 11.1 μg/dL had a specificity of 93% for a CST-60 >14.6 g/dL. Using historical levels of CST-60 ≥ 18.0 μg/dL, there would be 17% false positives requiring unnecessary dynamic testing.

In this community setting with low risk of AI (16%), a baseline AM cortisol of 11.1 μg/dL can reliably preclude the need for a CST-60. Clinicians should be aware of the new cutoffs for the assays available to them when evaluating patients for AI.