'Being disabled' as an exclusion criterion for clinical trials: a scoping review

People with disabilities (PWDs) are often excluded from biomedical research, but comprehensive data regarding their participation in clinical trials are not available. The objective of this study was to assess the rates of exclusion of PWDs from recent medical scientific research.

The protocol of the study was designed according to PRISMA-ScR (PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) extension for Scoping Reviews) guidelines. All completed interventional clinical trials registered on ClinicalTrials.gov between 2010 and 2020 regarding the 10 leading causes of global disability-adjusted life-years according to the Global Burden of Disease Study were analysed. An exclusion criterion from the study was considered explicit if it could be associated with one of the following seven categories: disability, physical impairment, cognitive impairment, behavioural or psychiatric disorders, language and communication impairment, sensory impairment. Comorbidities not more clearly defined and researcher discretion regarding exclusion of study participants were considered to be 'implicit exclusion criteria'. We assessed the appropriateness of explicit exclusion criteria in relation to the primary objectives of the trials and labelled them as 'absolute', 'relative' or 'questionable'.

The total number of trials analysed was 2710; 170 were paediatric trials (6.3%), 2374 were adult trials (87.6%) and 166 were trials including subjects of all ages (6.1%). Explicit exclusion criteria were found in 958 trials (35.3%). The disability category most frequently excluded was behavioural or psychiatric disorders, present in 588 trials (61.4%). In only 3% and 1% of the trials, the exclusion criteria were considered either 'absolute' or 'questionable', while in 96% the exclusion criteria were judged as 'relative'. Implicit exclusion criteria were present in 1205 trials (44.5%).

This study highlights the high rate of exclusion of PWDs from biomedical research and the widespread use of ill-defined exclusion criteria in clinical trials. It underscores the importance of more inclusive study designs so that PWDs can become active participants in research.