How have we measured trial outcomes of asthma attack treatment? A systematic review.

Background: Asthma attacks are a common problem for people with asthma and are responsible for significant healthcare costs. There is interest in a precision medicine approach to treatment. However, the choice of trial outcome measures for asthma attack treatment is hampered by the absence of a consensus on suitability. We carried out a systematic review to understand the characteristics of outcome measures used in randomised controlled trials of asthma attack treatment. Have randomised controlled trials of asthma attack treatment measured outcomes that are useful to patients and healthcare providers? Methods: The protocol was registered on PROSPERO (CRD42022311479). We searched for randomised controlled trials comparing treatments for adults with asthma attacks, published in English between 1972 and 2022 on MEDLINE, Embase and Cochrane Library databases. We recorded the outcome measures and study characteristics. Results: We identified 208 eligible randomised controlled trials from 35 countries. Trials ranged from 12 to 1109 participants, with a median of 60. The most common settings were the emergency department (n=165) and hospital admission (n=33). Only 128 studies had primary and secondary outcomes defined clearly. In those that did, 73% of primary outcomes measured change in lung function or other physiological parameters over a short period (usually <24 h). Patient-reported and healthcare utilisation outcomes were the primary outcome in 27%. Conclusions: Outcomes in randomised controlled trials of asthma attack treatment focus on short-term changes in lung function and may not capture patient-centred and economically important longer-term measures. More work is needed to investigate patient and other stakeholder preferences on core outcome sets.