A randomized, embedded trial of pre-notification of trial participation did not increase recruitment rates to a falls prevention trial

Objectives: To design and evaluate the effectiveness of a pre-notification leaflet about research to increase recruitment to a randomised controlled trial (RCT). Methods: A methodological, two arm, randomised controlled trial was conducted, embedded within an existing cohort RCT (REFORM). Participants were randomised for the embedded trial, using a 1:2 (intervention:control) allocation ratio, prior to being randomised for the REFORM RCT. Controls received a trial recruitment pack. The intervention group received an additional pre-notification leaflet 2 to 3 weeks before the recruitment pack. Primary and secondary analyses were conducted using relative risk, the Cox Proportional Hazards Model and Incremental Cost Effectiveness Ratios. Results: Of the 1,436 intervention group participants, 73 (5.1%) were randomised into the REFORM trial compared to 126 (4.4%) of the 2,878 control group participants. The associated relative risk (1.16) was not statistically significant (95% CI 0.88 - 1.56). The leaflet did not significantly increase return rate (RR 1.10, 95% CI 0.92 -1.28) or decrease time to return (Hazard Ratio: 1.11, 95% CI 0.93 -1.33). Incremental Cost Effectiveness Ratios indicated that the intervention may be cost-effective if the true estimate of effect were close to the upper bound of the associated 95% CI. Conclusion: A pre-notification leaflet to potential trial participants demonstrated a small difference in favour of the intervention with regards randomisation (0.7% difference) and return rates (1.1% difference).Results should however be interpreted with caution as confidence intervals for these estimates cross the point of no effect. Nevertheless, this research enhances existing evidence for pre-notification to increase recruitment rates, with further development and assessment of this potentially cost-effective intervention being recommended.