Design: Randomised placebo-controlled trial (RCT).

Allocation: 1:1 ratio of intervention:placebo using permuted-block assignment stratified by clinical centre.

Setting: 19 American Lung Association Asthma Clinical Research Center sites from April 2007 to April 2011.

Patients: Children aged 6–17 years (mean 11 years) with physician and lung function confirmed poorly controlled asthma, all of whom had been treated with inhaled corticosteroids for at least 8 weeks prior to enrolment. Patients with current or previous gastro-oesophageal reflux disease requiring treatment were excluded. A subgroup of 115 received pH studies.

Intervention: 149 children received lansoprazole (15 mg/day <30 kg or 30 mg/day >30 kg) and 157 received placebo.

Outcomes: Primary outcome—Change in Asthma Control Questionnaire (ACQ) score. Secondary outcomes—Rate of episodes of acute asthma, asthma symptom utility index, asthma control test for adolescents, asthma-specific quality of life for children score, meaningful clinically important changes in lung function tests, gastrointestinal symptoms or nocturnal awakenings.

Follow-up period: …