Meta-analysis of controlled trials of drug therapy in mild chronic asthma: the role of inhaled corticosteroids

OBJECTIVE: To determine the role of inhaled corticosteroids in the treatment of mild chronic asthma. SOURCE OF STUDIES: Searches of MEDLINE and Index Medicus for English language literature dealing with asthma and inhaled corticosteroids. DESIGN: All retrieved articles were subjected to predetermined criteria for inclusion in the meta-analysis. Inclusion criteria centered around randomized, double-blind studies reporting objective clinical endpoint(s) for subjects with mild chronic asthma who were treated for more than seven days. Studies that were included were not allowed to have any predetermined exclusion criteria. RESULTS: The literature search identified 129 articles, of which 41 satisfied some but not all of the criteria for inclusion. Five articles met all the criteria and were subjected to meta-analysis. The total number of subjects was 141. Peak expiratory flow rate (PEFR) was used as the objective endpoint for effect size calculation. Subjecting these five studies to quality review revealed a range of 0.607-0.741, with 1 as the highest attainable quality and 0 the lowest. Reported results for the different studies were found to be homogenous, thus allowing for the calculation of overall effect size. Inclusion of children in some of the studies added variance to the reported studies, but not to the point at which studies would be considered heterogenous. Effect sizes ranged between 0.41 and 0.89, and the overall weighted average effect size for PEFR was 0.59, with the calculated 95 percent confidence interval at 0.32 to 0.84. A tabulated display of binomial effect size for included trials provided ranges of success rates for treatment versus control values. Results of the studies were judged robust, as 92 studies reporting no significant effects are needed to turn the finding of the meta-analysis insignificant. CONCLUSIONS: Based on the results of the meta-analysis, the existing literature suggests a role for inhaled corticosteroids in the treatment of mild chronic asthma.

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