LAUSR

Background Significant minority of asthmatics develop severe disease with increased morbidity and risk of mortality. However, the mode of the onset of severe asthma is not well understood. Aim To study the events leading up to severe asthma in patients referred to a tertiary severe asthma centre. Methods Consecutive new patients referred to our centre between (….) undergone systematic assessment to confirm asthma diagnosis and establish severity level. Patients completed structured questionnaire narrating the mode and timing of the severe onset. Results 148 patients with confirmed severe asthma diagnosis included in the analyses (70% females, mean age 45.2yrs (16–94), FEV1% predicted 70.3±22, FEV1/FVC ratio 65±15, BMI 32±7.7 kg/m2, blood eosinophils 478 cells/µl, smokers: never 69%, ex 28% and current 4%). The mean age of onset of asthma was 19.4yrs (0–65), with majority [122 (82.4%)] had an early onset asthma (<40yrs), and minority [26 (17.6%)] had late onset asthma (≥40yrs). The mean duration of asthma prior to the onset of severe disease was 17.3yrs (0–57), and 25/146(17%) started as denovo severe. The transformation into severe disease was of gradual progression in 67/143(47%), following an acute lower respiratory tract infection in 46/143 (32%), or non-infective other acute event (multiple causes: e.g. accidental inhalation injury, psychological stressful event) in 30/143 (21%). The clinical outcomes in terms of lung function, biomarkers or asthma control did not differ significantly between these 3 modes of onset. Conclusion The mode of severe asthma onset is variable with majority of patients endure gradual progression from mild to severe, whilst about third transform into severe following an infective event. Longitudinal studies are warranted to elucidate triggers of severity transformation and enable early intervention or prophylactic measures to prevent disease progression.