S63\u2005Adherence, airway inflammation and adrenal function in a cohort of paediatric asthma patients

Abstract

Introduction Systemic absorption of inhaled corticosteroids (ICS) is greater in healthy adults than asthmatics [Lancet 2000;356:556]. ICS are the mainstay of paediatric asthma treatment, however adverse effects can occur. The incidence of adrenal suppression in children with asthma treated with ICS is unknown. There are case reports of deaths in children with asthma with undiagnosed adrenal suppression; the dose at which adrenal suppression occurs is not known. Aim/Short hypothesis We hypothesized adrenal suppression for a given dose of ICS is less in asthmatic children with worse airway obstruction and inflammation. We investigated the relationship between airway obstruction, airway inflammation and adrenal function and objectively defined dose of ICS inhaled. Methods Single centre prospective cohort study of children aged 4–16years prescribed >400 micrograms/day beclomethasone (BDP) equivalent. 46 children with asthma, median age 11.6years (range 9.5–14.0years) were recruited and issued an electronic monitoring device (EMD) to record adherence to ICS. After the monitoring period, a low dose short Synacthen test (LDSST) was performed, with baseline cortisol level taken at 0 minutes prior to administration of 300ng/m2 Synacthen, and response assessed with serial plasma cortisol levels taken at 15, 20, 25, 30 and 35 minutes post-administration. (Normal result baseline cortisol >100nmol/L increasing to >500nmol/L). Results EMD data were available in 24 patients in the period prior to LDSST. 12 had normal and 12 abnormal Synacthen tests. There were no significant differences in airway obstruction, adherence to ICS, or average daily dose of ICS taken for a median of 71 (62–121) days prior to the test (based on EMD data). FeNO was significantly higher in children with a normal Synacthen test (p=0.002). Symptom scores were lower and blood eosinophils were higher in children with normal adrenal function, but this was not significant. Conclusions Children with normal adrenal function had significantly higher FeNO, suggesting ongoing airway inflammation. Although not significantly different, they also had lower median adherence to ICS, suggesting this may be the explanation. However, inflammation causes increased bronchial blood flow, therefore more systemic absorption of ICS and more adrenal suppression would be expected. As adrenal function remains normal, this group of children may exhibit steroid insensitivity and have poor symptom control.Abstract S63 Table 1 Normal Synacthen n=12 Abnormal Synacthen n=12 Significance Dose of ICS prescribed (mcg BDP equivalent/day) 1000 (850–1000) 800 (800–1000) Ns Asthma control test (ACT) score 15 (12–20) 18 (15–21) Ns Overall adherence (%) 57 (43–88) 70 (59–80) Ns Average dose of ICS taken based on EMD data 490 (282–887) 615 (471–810) Ns FEV1% predicted 85 (74–99) 87 (80–107) Ns FEV1:FVC 0.96 (0.77–1.00) 0.90 (0.82–1.00) Ns Bronchodilator reversibility (BDR) (%) 7 (3–26) 19 (11–32) Ns FeNO ppb 67 (37–87) 16 (6–34) p=0.002 Blood eosinophils x109/L 0.7 (0.5–0.9) 0.5 (0.2–0.9) Ns