Randomised controlled trials (RCTs) that compared inhaled corticosteroids with montelukast or with inhaled corticosteroids plus montelukast in patients (aged less than 18 years) with a clinical diagnosis of asthma for at least six months before entry into the trial, were eligible for inclusion. The treatment had to last at least four weeks and the dose of inhaled corticosteroids had to be maintained throughout the intervention period. Trials published in abstract form were excluded.
The primary outcome was asthma exacerbations, defined as worsening symptoms requiring systemic corticosteroid use. Secondary outcomes included final pulmonary function (defined as forced expiratory volume in the first second - FEV1), hospitalisation due to asthma exacerbations, adverse events, and adherence.
In included trials, the inhaled corticosteroids assessed were budesonide, beclomethasone, fluticasone propionate, and triamcinolone. The dose of inhaled corticosteroids was 200 to 300μg/day of beclomethasone or equivalent; the dose of montelukast was 5 to 10mg/day. No trials used additional anti-asthmatic drugs, other than rescue beta2-agonists and oral corticosteroids. The mean age of included patients was 9.7 years, 63% were male (range 54 to 80%), and their baseline FEV1 was 81% (range 64 to 98%). The trials included multicentre and crossover trials. Most of the included trials were funded by pharmaceutical companies (where reported).
Two reviewers independently applied the inclusion criteria; there were no disagreements.