Inadequate assessment of adherence to maintenance medication leads to loss of power and increased costs in trials of severe asthma therapy: results from a systematic literature review and modelling study.

Adherence to inhaled maintenance therapy in severe asthma is rarely adequately assessed, and its influence on trial outcomes is unknown. We systematically determined how adherence to maintenance therapy is assessed in clinical trials of "add-on" therapy for severe asthma. We model the improvement in trial power that could be achieved by accurately assessing adherence.A systematic search of six major databases identified randomised trials of add-on therapy for severe asthma. The relationship between measuring adherence and study outcomes was assessed. An estimate of potential improvements in statistical power and sample size was derived using digitally recorded adherence trial data.87 randomised controlled trials enrolling 22 173 participants were included. Adherence assessment was not reported in 67 trials (n=13 931, 63%). Studies that reported adherence used a range of self-report and subjective methods. None of the studies employed an objective assessment of adherence. Studies that reported adherence had a significantly reduced pooled variance in forced expiratory volume in 1 s (FEV

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Copyright ©ERS 2019.

Déclaration de conflit d'intérêts

Conflict of interest: M.C. Mokoka has nothing to disclose. Conflict of interest: M.J. McDonnell has nothing to disclose. Conflict of interest: E. MacHale has nothing to disclose. Conflict of interest: B. Cushen has nothing to disclose. Conflict of interest: F. Boland has nothing to disclose. Conflict of interest: S. Cormican has nothing to disclose. Conflict of interest: C. Doherty has nothing to disclose. Conflict of interest: F. Doyle has nothing to disclose. Conflict of interest: R.W. Costello has nothing to disclose. Conflict of interest: G. Greene has nothing to disclose.