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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