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Table 2 Potential risk factors and protective factors for trial discontinuation due to slow recruitment

From: Learning from failure - rationale and design for a study about discontinuation of randomized trials (DISCO study)

Modifiable factors Non-modifiable Factors
Risk Protective Risk Protective
Burdensome data collection at recruiting sites Support from a methods centre, clinical trials unit, or contract research organization Placebo control Active treatment as control
No professional staff at recruiting centres to manage the trial Paid local staff at recruiting centres, dedicated central trial coordinator, patient involvement in trial planning and/or conduct No external funding Externally funded or fully Industry sponsored
No projection of recruitment rates Projection of patient recruitment based on e.g. pilot trial applying the full protocol or other checks for eligible patient volume Long duration of follow-up Short duration of follow-up / High community interest in research topic (e.g. new technology or new treatment)
No consideration of recruitment strategies Consideration of recruitment support strategies (e.g. regular visits/audits by PI; specific training held for recruiting staff; regular progress reports; posters and information leaflets etc.) No research network, low trial experience Experienced PI/steering committee/network of recruiting centres for RCTs
Single centre trial Multicentre trial Equivalence/non-inferiority design Intervention only available through trial participation
Low motivation for recruiting sites Financial incentives for recruiting staff and participants Critically ill or paediatric patients as target population Trial experience with certain vulnerable trial populations