Recruitment and retention of participants in randomised controlled trials: a review of trials funded and published by the United Kingdom Health Technology Assessment Programme
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BACKGROUND: Substantial amounts of public funds are invested in health research worldwide. Publicly funded randomised controlled trials (RCTs) often recruit participants at a slower than anticipated rate. Many trials fail to reach their planned sample size within the envisaged trial timescale and trial funding envelope. OBJECTIVES: To review the consent, recruitment and retention rates for single and multicentre randomised control trials funded and published by the UK's National Institute for Health Research (NIHR) Health Technology Assessment (HTA) Programme. DATA SOURCES AND STUDY SELECTION: HTA reports of individually randomised single or multicentre RCTs published from the start of 2004 to the end of April 2016 were reviewed. DATA EXTRACTION: Information was extracted, relating to the trial characteristics, sample size, recruitment and retention by two independent reviewers. MAIN OUTCOME MEASURES: Target sample size and whether it was achieved; recruitment rates (number of participants recruited per centre per month) and retention rates (randomised participants retained and assessed with valid primary outcome data). RESULTS: This review identified 151 individually RCTs from 787 NIHR HTA reports. The final recruitment target sample size was achieved in 56% (85/151) of the RCTs and more than 80% of the final target sample size was achieved for 79% of the RCTs (119/151). The median recruitment rate (participants per centre per month) was found to be 0.92 (IQR 0.43-2.79) and the median retention rate (proportion of participants with valid primary outcome data at follow-up) was estimated at 89% (IQR 79-97%). CONCLUSIONS: There is considerable variation in the consent, recruitment and retention rates in publicly funded RCTs. Investigators should bear this in mind at the planning stage of their study and not be overly optimistic about their recruitment projections.
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A review of 151 trials from 2004 to 2016 funded by the UK Health Technology Assessment Programme found that 44% did not reach their recruitment targets.
“For example, a review of 151 trials from 2004 to 2016 funded by the UK Health Technology Assessment Programme found that 44% did not reach their recruitment targets.311”
From SPIRIT 2025 explanation and elaboration: updated guideline for protocols of randomised trials (2025) · cites this paper as [311]
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- Authors
- Walters, S. J., Bonacho dos Anjos Henriques-Cadby, I., Bortolami, O., Flight, L., Hind, D., Jacques, R. M., Knox, C., Nadin, B., Rothwell, J., Surtees, M., & Julious, S. A.
- Affiliations
- University of Sheffield (GB)
- Corresponding author
- Walters, Stephen J
- ORCID
- Venue
- BMJ Open
- Publisher
- BMJ
- Published
- 2017-03
- Volume
- 7
- Issue
- 3
- Pages
- e015276
- ISSN
- 2044-6055 (ISSN-L)
- PMC
- PMC5372123
- OpenAlex
- W2603257905
- Cited by
- 560
- References
- 49
- Citations by year
- 2026: 34 · 2025: 65 · 2024: 65 · 2023: 77 · 2022: 97 · 2021: 84 · 2020: 79 · 2019: 33 · 2018: 22 · 2017: 4
- FWCI
- 35.81
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Licence
- cc-by-nc
- Locations
- BMJ Open (publishedVersion, cc-by-nc)
- PubMed Central (publishedVersion, cc-by-nc)
- PubMed (publishedVersion)
- White Rose Research Online (University of Leeds, The University of Sheffield, University of York) (acceptedVersion)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
- HighWire Press Open Archive (submittedVersion)
- Research Explorer (The University of Manchester) (submittedVersion)
- Funders
- National Institute for Health and Care Research
- Topics
- Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Ethics in Clinical Research
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Clinical Trials
- Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
- Keywords
- participant recruitment, participant retention, randomized controlled trials, trial size, recruitment rate, consent rates, trial planning
- MeSH terms
- Cost-Benefit Analysis, United Kingdom, Humans, Patient Dropouts, Technology Assessment, Biomedical, Multicenter Studies as Topic, Randomized Controlled Trials as Topic, Patient Selection
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