EnTraP: A Factorial Randomised Controlled Trial embedded within WHiTE 8 COPAL investigating the effect of an Enhanced Trainee Principal Investigator Package and Digital Nudge on recruitment rates.

Background Studies evaluating interventions to improve recruitment aimed at recruiters to the trial are limited. The primary aim was to evaluate the effectiveness of an educational intervention to Trainee Principal Investigators (TPI) and a positive reinforcement intervention via a digital nudge on recruitment to the WHiTE 8 COPAL trial. Design This was a multicentre, open, cluster, 2x2 factorial RCT embedded in the WHiTE 8 COPAL RCT, in which research sites were randomised 1:1:1:1 to receive the enhanced TPI package, the digital nudge intervention, both, or neither. Results 1215 patients were recruited to the WHiTE 8 COPAL trial across 20 sites between August 2018 and March 2019. There was a statistically significant interaction between the interventions (IRR 2.09, 95% CI 1.64 to 2.68, p < 0.001). There was a statistically significant benefit on recruitment (IRR 1.23 95% 1.09 to 1.40, p=0.001) from utilizing an enhanced TPI education intervention. The digital nudge intervention had no significant impact on recruitment (IRR 0.89 95% CI 0.79 to 1.01, p=0.07). Within enhanced TPI package sites, the digital nudge had a beneficial effect, while in the standard practice TPI sites it had a detrimental effect. Discussion An enhanced TPI package involving an education and support programme was effective in increasing recruitment in the first six months of trial commencement. There was no evidence for the effectiveness of the digital nudge intervention in isolation, though our results show that when combined with an education programme it leads to enhanced effectiveness of that programme.