ESPE Abstracts

Background and aims: The low dose short corticotropin test (LCT) is the most frequently used test to diagnose glucocorticoid-induced adrenal insufficiency (GAI) in children. Result of the LCT must be interpreted with caution since stimulated peak cortisol (PC) thresholds depend on the assay and time of sampling. We evaluated the prevalence of GAI by the LCT using both 20 and 30 minutes sampling and cortisol measurements by the most recent Roche Elecsys Cortisol II assay in children who had been treated with high dose oral (>20 mg/m² hydrocortisone converted dose) synthetic glucocorticoids for at least 4 weeks (HDSG). In addition, we investigated the relationship between PC and age, BMI SDS, basal cortisol (BC) at testing and time since stopping glucocorticoid treatment.

Methods: Clinical and laboratory data on 28 children, who underwent a LCT using 1 µg /m² Synacthen between 08.00 and 9.00 h AM in fasting condition between 01-2016 and 08-2022, were retrieved. Cortisol was measured by the Cobas 8000 e801/Roche Diagnostics assay (intra-assay CV of 1.9-2.8%). Both a PC <160 µg/L and a PC <135µg/L were used for the definition of GAI.

Results: In all children, the LCT was performed at least 4 weeks after stopping glucocorticoid treatment: in 5/28 for asthma, in 6/28 for bronchopulmonary dysplasia, in 2/28 for rheumatic arthritis. PC was observed at 20 minutes in 2/28 (7.1%) and at 30 minutes in 25/28 (89.3%) children. In total, 10/28 (35.7%) had a BC < 60 µg/L, while 13/28 (46.4%) had a PC <160 µg/L and 7/28 (25%) had a PC <135µg/L. Mean PC was not different between boys and girls (169 µg/L vs 160µg/L, P= 0.782) or between the studied diseases. PC correlated significantly with BC (r= 0.502, P= 0.007). PC did not correlate significantly with age, BMI z-score at testing and time since stopping glucocorticoid treatment. A BC >120µg/L predicted a PC >160 µg/L, while all children with a BC >65 µg/L had a PC >135µg/L.

Conclusion: Almost half of the HDSG treated children had GAI when using the commonly used PC cut-off, compared to only a quarter when using the newly proposed lower cut-off for the Elecsys Cortisol II assay. Considering a GAI by a PC <135 µg/L, LCT might not be of additional value in children presenting with a basal cortisol >65µg/L after stopping glucocorticoid treatment, irrespective of their underlying disease and age.