Diagnostic performance of morning serum cortisol for glucocorticoid weaning in children and adults

Design

Morning cortisol predicts the outcome of the short synacthen test (SST). There is a paucity of studies examining this in a dedicated cohort of children and adults weaning off glucocorticoids and using a modern immunoassay. This study aimed to identify early morning serum cortisol (EMC) cut-offs which predict the SST outcome in children and adults during glucocorticoid weaning.

Methods

A retrospective cohort study of pediatric and adult patients on long-term glucocorticoids with suspected glucocorticoid-induced adrenal insufficiency (GIAI) undergoing an SST. Our main outcomes were cut offs with 95% and 99% sensitivity and specificity for EMC analysed on modern immunoassays, determined via receiver operating characteristic (ROC) curve analysis. A pass on SST was defined as 30-min cortisol of ≥430 nmol/L (15.6 µg/dL).

Results

151 and 372 SSTs were included in the pediatric and adult cohorts, respectively, of which 32% and 37% were passed. ROC curve analysis demonstrated that EMC performed well in both cohorts with area under curve (AUC) of 0.79 (95% CI, 0.71, 0.87) and 0.88 (95% CI, 0.84, 0.91), respectively. EMC cut offs to predict a pass on SST were 278 (10.1 µg/dL) and 290 nmol/L (10.5 µg/dL) at 95% sensitivity, and 316 (11.5 µg/dL) and 349 nmol/L (12.7 µg/dL) at 99% sensitivity, respectively. Further analysis in adults showed that using a 95% cut off in clinical practice was effective as 48/51 patients with EMC between 290 and 349 nmol/L (10.5-12.7 µg/dL), were weaned off without adverse events.

Conclusion

Morning serum cortisol can predict the SST outcome in children and adults weaning from glucocorticoids. An EMC > 290 nmol/L in adults predicts a patient can stop glucocorticoid therapy and will recover adrenal function.