Researchers often worry about how hard it can be to recruit people into clinical studies. After months of preparation, participant numbers can grow frustratingly slowly.
So when our latest eczema study filled up much faster than expected, we thought we had hit the jackpot.
The Scratch Less Study, part of the RAPID Eczema Trials programme, opened to participants on 1 June 2026. The study was designed with input from members of our Rapid Eczema Trials community and is entirely online, making it easy to take part. It consists of two linked studies – one for people aged 13 years and older and one for children aged 8 to 12 years old. What surprised us was just how much interest there was. Within just two months, we had reached our target of 278 participants in the study for people aged 13+ years.
While this was great news, it also created some unexpected challenges.
When recruitment happens over a longer period, researchers can keep an eye on who is joining the study and adjust their approach if certain groups are under-represented. Because our recruitment was so rapid, we had little opportunity to do this. Early signs suggested we had recruited fewer men and there was less diversity in terms of ethnicity and socioeconomic groups than we had hoped for.
Another challenge was that participants are followed for 16 weeks. By the time recruitment reached its target, no one had completed the study, so we had very little information about how many people would stay involved or how closely they would follow the Scratch Less programme.
Our recruitment methods also ended up being different from what we had planned. We expected many participants to come through GP practices, but recruitment happened so quickly that most practices had not yet begun contacting potential participants. Instead, most people joined from our eczema community networks and social media. In fact, social media advertising worked so well that we stopped it after just one week.
The rapid response also put pressure on the study team. Tasks that would normally be spread over several months had to be completed in a much shorter time.
After discussing the situation with our oversight committees, we decided to apply for permission to continue recruiting beyond the original target. This would help us improve the diversity of the study population and give us more confidence in our assumptions about participant engagement and follow-up.
Even that was not straightforward. Increasing the sample size required formal approval, highlighting the fact that research governance systems are not always designed for studies that recruit exceptionally quickly. By the time approvals were in place, we had already gone beyond our original target.
Looking back, I am delighted that so many people wanted to take part. A larger study should give us more reliable results and help us better understand which approaches work best for different people. We will continue recruiting into the study for people 13+ years until the end of September and are still very keen to enrol children aged 8 to 12 years, as we haven’t yet reached our target for that group.
Most researchers are familiar with the challenge of recruiting too slowly. Our experience with the Scratch Less Study shows that, occasionally, success can create a different challenge altogether: managing a study that is popular beyond expectations.
Professor Kim Thomas
Co-lead for the Rapid Eczema Trials project