Should recommendations about starting inhaled corticosteroid treatment for mild asthma be based on symptom frequency: a post-hoc efficacy analysis of the START study

Summary Background Low-dose inhaled corticosteroids (ICS) are highly effective for reducing asthma exacerbations and mortality. Conventionally, ICS treatment is recommended for patients with symptoms on more than 2 days per week, but this criterion has scant evidence. We aimed to assess the validity of the previous symptom-based cutoff for starting ICS by establishing whether there was a differential response to budesonide versus placebo for severe asthma exacerbations, lung function, and asthma symptom control across subgroups identified by baseline asthma symptom frequency. Methods We did a post-hoc analysis of the 3 year inhaled Steroid Treatment As Regular Therapy (START) study, done in 32 countries, with clinic visits every 3 months. Patients (aged 4–66 years) with mild asthma diagnosed within the previous 2 years and no previous regular corticosteroids were randomised to receive once daily, inhaled budesonide 400 μg (those aged 1 to ≤2 symptom days per week, 0·57 [0·41–0·79] >2 symptom days per week, pinteraction =0·94), and the decline in postbronchodilator lung function was less at 3 years' follow-up (pinteraction =0·32). For budesonide versus placebo, severe exacerbations requiring oral or systemic corticosteroids were reduced (rate ratio 0·48 [0·38–0·61] 0–1 symptom days per week, 0·56 [0·44–0·71] >1 to ≤2 symptom days per week, and 0·66 [0·55–0·80] >2 symptom days per week, pinteraction =0·11), prebronchodilator lung function was higher, and symptom-free days were more frequ