Table 1.

Limitations of traditional randomised controlled trials in interstitial lung disease

	Typical limitations
Trial design	Need for large, fixed and dedicated sample sizes to independently address each research question or intervention in separate studies Fixed study duration Lack of generalisability of data from homogeneous study cohorts to real-world populations Equally likely for patients to receive control or active treatment Limited incentive to design head-to-head trials of approved treatments
Operational factors	Site related: Infrastructural barriers to conducting clinical trials in a broad and diverse geographical area, particularly in small centres and under-resourced settings (reduced equity) Sponsor related: High operational costs, including costs to build study infrastructure for each trial and support extensive tests that fall outside patient care Study related: Lack of open data Slow identification of new successful interventions Delays in translating results into clinical practice
Patient factors	Extensive inclusion and exclusion criteria and disease-specific focus (reducing opportunities to participate and equity of access to new treatments/interventions) Burden of patient schedule, including additional travel requirements Limited access to trials and increased inequality due to frequent focus on only a few specialist trial sites