Exclusion debt: what it costs to leave people out of clinical research.
Definition. Exclusion debt is the compounding cost of designing and running clinical research without the people it's meant for. Missed recruitment targets, extra months, referrals nobody answers, and research that never reaches the places where illness is most common are all repayments of it. Like technical debt, it's cheap to avoid early and expensive to pay later.
How it shows up in UK research
Of NIHR-funded clinical trials reported from 2017 to 2020, nearly 4 in 10 didn't reach their original recruitment target, and 37% needed more time.
Jacques et al., BMJ Open, 2022.
From 2013 to 2018, the areas of England with the most long-term illness had the fewest people taking part in research. To match, about 90,000 people would have had to be recruited in different areas.
NIHR Evidence, on Bower et al., September 2020.
When the Health Research Authority checked 398 applications given a favourable ethics opinion in 2023, about a quarter hadn't involved the public at all.
HRA, Public involvement in health and social care research in the UK: report 2023.
Referrals that go unanswered add to it too. No published figure covers UK commercial clinical trials, but in a 2017 Tufts survey of 2,000 doctors and nurses, mainly in the US and Europe, nearly 30% of doctors and 45% of nurses said they never heard back after referring a patient to a clinical trial (Tufts CSDD, in Applied Clinical Trials, January 2017).
What the UK rules say, and don't
The HRA expects public involvement in all research. Participant information developed without it "will not normally receive a favourable opinion" from an NHS ethics committee.
The new UK clinical trials regulations came into force on 28 April 2026. The HRA's diversity and inclusion guidance "is not a legal requirement", and its pilot of inclusion and diversity plans closed in December 2025.
Sources: HRA, public involvement guidance; HRA, clinical trials regulations.
Paying it down early
Shape it before it's final.
Members who live with the condition look at the protocol, the invitation and the visit plan, and tell you what would make the clinical trial worth joining, in words you can cite.
Follow every referral through.
Members who pass the screening questions and say yes are referred, and we check in with every one. You see which referrals went nowhere, and why.
We don't claim that following patients up raises enrolment: we haven't found controlled evidence that it does. It gives the team the facts, not a promised result.
Read more
The Exclusion Debt Report
One disease each month: who is missing from the evidence, and what it costs. Issue 1 is lung cancer.
Read the report NewsletterExclusion Debt
Our founder Ashish Rishi's newsletter on who clinical trials leave out, and what it costs.
Subscribe on Substack (opens in a new tab) Report · UK membersThe Frequency of Exclusion
What 1,204 people from underrepresented UK communities told us about clinical research and healthcare.
Explore the report (opens in a new tab) GuidesResources
Free UK guides and research for anyone recruiting or running clinical trials.
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