Identifying and appraising outcome measures for severe asthma: a systematic review

Valid outcome measures are imperative to evaluate treatment response, yet the suitability of existing endpoints for severe asthma is unclear. This review aimed to identify outcome measures for severe asthma and appraise the quality of their measurement properties.A literature search was performed to identify “candidate” outcome measures published between 2018–2020 (PROSPERO, CRD42020204437). A modified Delphi exercise was conducted to select “key” outcome measures within healthcare professional, patient, pharmaceutical, and regulatory stakeholder groups. Initial validation studies for “key” measures were rated against modified quality criteria from COnsensus-based Standards for the selection of health Measurement Instruments (COSMIN). The evidence was discussed at multi-stakeholder meetings to ratify “priority” outcome measures. Subsequently, four bibliographic databases were searched from inception to identify development and validation studies for these endpoints. Two reviewers screened records, extracted data, assessed their methodological quality, and graded the evidence according to COSMIN.96 outcome measures were identified as “candidates”, 55 as “key”, and 24 as “priority” for severe asthma; including clinical, healthcare utilisation, quality of life, asthma control, and composite. 32 studies reported measurement properties of 17 “priority” endpoints from the latter three domains. Only SAQ and C-ACT were developed with input from severe asthma patients. The certainty of evidence was “low” to “very low” for most “priority” endpoints across all measurement properties, and none fulfilled all quality standards.Only two outcome measures had robust developmental data for severe asthma. This review informed development of core outcome measures sets for severe asthma.