Phenotyping severe asthma attacks in patients hospitalised with acute asthma

Background: Asthma Attacks (AA) are common, heterogeneous events that can lead to hospital admissions. However, the biological and physiological characteristics of AA, alternate causes for admission, and nature of airway inflammation in AA are not well described. Aim: To describe patient and clinical characteristics, and feasibility of assessing point of care (POC) biomarkers of Lung Function (LF) and airway inflammation using oscillometry and exhaled nitric oxide (FeNO) in adult patients admitted to a secondary respiratory centre with suspected AA. Methods: Ongoing prospective clinical study recording patient characteristics, LF using Spirometry and Forced Oscillation Technique (FOT) and T2 biomarkers (blood eosinophil count and FeNO) in patients admitted with AA. Medical notes reviewed for treatment and other recorded diagnoses. All patients started bronchodilator (BD) and systemic corticosteroid (SCS) treatment prior to study assessment. Results: 51 patients recruited to date of whom 13 (25%) had no Evidence of Airflow Limitation (EAL). No significant demographic differences apparent between patients with and without EAL so far but those without EAL had a higher likelihood of a different primary diagnosis on discharge and a longer length of hospital stay (4.1 v 3.3 days). 14/51 (27%) of patients had raised T2 biomarkers but in those without EAL, only 1/13 had raised FeNO and all had normal BEC. 49/51 (96%) managed to perform FOT, and 46/51 (90%) performed FeNO. Conclusions: 25% of patients admitted with suspected AA had no EAL or raised T2 biomarkers but were still treated with BD and SCS. Alternative diagnoses should be considered, and treatment revised where there is limited evidence of acute asthma.