# What is the impact on recruitment of a shortened compared with a standard-length participant information leaflet? PROMETHEUS in IBD-BOOST: study within a trial, a decentralised UK randomised controlled trial

## TL;DR

This study compared shortened and standard-length information leaflets for recruiting participants to an online trial, finding no significant difference in recruitment or retention rates.

## Contribution

The study evaluates the impact of PIL length on recruitment and retention in a decentralized trial setting, offering insights into participant engagement strategies.

## Key findings

- Recruitment rates were 15.86% for standard PILs and 17.84% for shortened PILs, with no significant difference.
- Retention rates were not statistically different between the two PIL groups.
- Shortened PILs may be as effective as standard-length ones for recruitment and retention in online trials.

## Abstract

Participant Information Leaflets (PILs) are lengthy and increasingly complex, and could deter research participation. A shortened PIL may be more appealing as it is likely to provide a more a manageable volume of information. Previous research has found that shortened PILs are no less effective for recruitment outcomes, and we deemed it useful to replicate this in an online setting. We also decided to compare retention rates, given the potential for more information to increase participants’ motivation.

To evaluate the efficacy of a shortened vs standard-length PIL on trial recruitment and retention rates.

This two-arm study within a trial (SWAT) was embedded in a host randomised controlled trial (RCT)—IBD-BOOST.

Potential participants were randomised to receive a standard-length or shortened PIL electronically for recruitment to the host RCT. An ethics committee approved potential participants being blinded to this randomisation.

Primary outcome: The percentage of SWAT participants receiving the shortened vs standard PIL who were recruited to the RCT.

Four thousand two hundred one participants were randomised to the standard-length (n = 2099) and shortened (n = 2102) PIL arms. Thirty-four email queries were received about the PILs—18 from those who received the standard and 16 from those receiving the shortened. Seven hundred eight SWAT participants were recruited to the RCT—333 (15.86%) who received the standard-length PIL and 375 (17.84%) who received the shortened (OR = 1.15, (95%CI = 0.98, 1.35), p = 0.09). Retention rates in the RCT were not statistically different between groups.

We did not find evidence of a significant difference between RCT recruitment and retention rates in participants randomised to the standard-length PIL compared with the shortened. It may be that a shortened PIL has the same effect on recruitment and retention outcomes, providing that the trial does not require extensive information for other reasons (e.g. safety). Therefore, it could be argued that researchers have a choice about how long to make PILs, perhaps with a link to more detail. Alternatively, given that there was no benefit of the shortened PIL, it may be worth comparing written PILs with other methods of conveying information to determine optimal means of encouraging participation and retention in decentralised trials.

A randomised controlled trial of supported, online, self-management for symptoms of fatigue, pain and urgency/incontinence in people with inflammatory bowel disease: the IBD-BOOST trial (ISRCTN71618461 on ISRCTN registry).

The online version contains supplementary material available at 10.1186/s13063-025-08931-6.