SERUM MORNING CORTISOL AS A SCREENING TEST FOR ADRENAL INSUFFICIENCY.

Abstract

ABSTRACT Objective: To evaluate the performance of morning serum cortisol (MSC) compared to a 10 μg ACTH stimulation test in the diagnosis of adrenal insufficiency (AI). Methods: A retrospective, cross-sectional analysis of ACTH stimulation tests were conducted. From a total of 312 potentially eligible ACTH stimulation tests, 306 met the inclusion criteria. The population was randomised into two groups, test (n: 159) and validation (n: 147). In the test group, the ROC-curve test evaluated the diagnostic performance of MSC. Results: A subnormal cortisol response to ACTH was found in 25.8% of the test group. The AUC values of MSC to predict AI at +30, +60 or maximal cortisol response were 0.874, 0.897, and 0.925 (95% CI 0.81-0.92, 0.83-0.93 and 0.87-0.96). Youden index was 234.2 mmol/L with sensitivity of 83.3% (95% CI 65.2 to 94.3%), and specificity of 89.1% (95% CI 82.4 to 93.9%). Positive and negative predictive values were 64.1% (95% CI 47.1 to 78.8%) and 95.8% (95% CI 90.5 to 98.6%). There was no difference in age, gender, AI prevalence or mean serum cortisol at +30, +60 in the validation group, however, a lower mean MSC value was found. Lower sensitivity and specificity values (88.3%, 60%) were found for the 234.2 mmol/L cutoff value. Conclusion: This study supports the role of MSC as a first-step diagnostic test in patients with clinically suspected AI. The short stimulation test could be omitted in almost half of the cases. Prospective and longitudinal studies to reproduce and confirm the cutoff values proposed are warranted.