Early morning salivary cortisol and cortisone, and adrenal responses to a simplified low‐dose short S ynacthen test in children with asthma

Objective To examine serum cortisol responses to a simplified low‐dose short S ynacthen test ( LDSST ) in children treated with inhaled corticosteroids ( ICS ) for asthma and to compare these to early morning salivary cortisol ( EMSC ) and cortisone ( EMSC n) levels. Design Early morning salivary cortisol and EMSC n samples were collected for three consecutive days. On day three, S ynacthen 500 ng/1·73 m 2 was administered intravenously. Samples were collected at 0, 15, 25, 35 min. Results A total of 269 subjects (160 M: 109 F), median (range) age 10·0 (5·1–15·2) years were studied. Peak cortisol in the LDSST was <500 nmol/l in 101 subjects (37·5%) and <350 nmol/l in 12 subjects (4·5%). Basal cortisol correlated with peak cortisol: r  = 0·55, (95% CI : 0·46, 0·63, P  < 0·0001). Time at which peak cortisol concentration was achieved was significantly related to the value of peak cortisol ( P  < 0·0001), with higher cortisol peaks occurring later in the test and lower cortisol peaks occurring earlier. EMSC and EMSC n had no predictive value for the identification of patients with a peak cortisol <500 nmol/l. EMSC n was superior to EMSC in identifying patients with a peak cortisol <350 nmol/l: a minimum EMSC n cut‐off value of 12·5 nmol/l gave a negative predictive value of 99·2% and positive predictive value of 30·1%. Conclusion Our data illustrate that basal measures of cortisol are likely to be of value in screening populations for patients at greatest risk of adrenal crisis. EMSC n shows promise as a screening tool for the identification of patients with severe adrenal insufficiency.