The biochemical diagnosis of adrenal insufficiency with modern cortisol assays: Reappraisal in the setting of opioid exposure and hospitalization

OBJECTIVE: We aimed to (1) examine the diagnosis of opioid-induced adrenal insufficiency, and (2) investigate the diagnostic value of a morning cortisol <83 nmol/L (3 µg/dl) for the diagnosis of adrenal insufficiency, using newer more specific cortisol assays and cut-offs. DESIGN: Retrospective study (5/2015-10/2020). PARTICIPANTS: Cohort 1 (N = 75): adults who underwent cosyntropin stimulation testing and opioid exposure for >30 days. Cohort 2 (N = 854): adults, with or without opioid exposure, who had a morning cortisol level measured the same day as stimulation testing. MEASUREMENTS: Peak cortisol during cosyntropin stimulation testing. Sensitivity and specificity of morning serum cortisol for adrenal insufficiency. RESULTS: The prevalence of adrenal insufficiency in patients with chronic opioid exposure who underwent cosyntropin stimulation testing was 4.0% using a cortisol cutoff of <405 nmol/L (14.7 µg/dl) versus 19% using the traditional cutoff of <500 nmol/L (18.1 µg/dl). For hospitalized patients with and without opioid-exposure, 14 of 22 (64%) patients with morning cortisol levels of <83 nmol/L (3 µg/dl) passed cosyntropin stimulation testing. A morning cortisol level of <348 nmol/L (12.6 µg/dl) had 100% sensitivity (95% confidence interval: 84.5%-100%) for the diagnosis of adrenal insufficiency. CONCLUSION: Applying a cutoff of <405 nmol/L (14.7 µg/dl), opioid-induced adrenal insufficiency is rare. Nearly 1 out of 6 patients would be reclassified as having adrenal insufficiency applying the guideline-recommended cutoff of <500 nmol/L (18.1 µg/dl). Serum morning cortisol <83 nmol/L (3 µg/dl) is not a valid diagnostic test for adrenal insufficiency in hospitalized patients, whether or not receiving opioids.