ReviewBMJ open2022
Recruitment, consent and retention of participants in randomised controlled trials: a review of trials published in the National Institute for Health Research (NIHR) Journals Library (1997-2020).
Review in BMJ open, 2022. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 79 papers, 5 of them syntheses that pooled it.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
79 citing papers in PubMed, 5 syntheses or guidelines pooled it.
- Strategies to improve recruitment to randomised trials.The Cochrane database of systematic reviews · 2026Pooled it
- Pooled it
- Recruitment and Retention Strategies for Randomized Clinical Trials Involving Family Members of ICU Patients.Critical care explorations · 2024Pooled it
- Pooled it
- Recruitment and retention interventions in surgical and wound care trials: A systematic review.PloS one · 2023Pooled it
- Feasibility study of a novel mHealth clinical decision support application to enable community health workers to manage hypertension in rural Guatemala.Journal of global health · 2026Trial
- SWAT 116: the effectiveness of an infographic to improve trial recruitment-a randomised study within a trial (SWAT).Trials · 2026Trial
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- Trial
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- Trial
- Implementing a patient-oriented pole walking intervention in retirement homes: A non-randomized feasibility trial.PloS one · 2026Trial
- Recruitment and retention in a preclinical AD trial: comparisons between academic and non-academic sites.Alzheimer's research & therapy · 2025Trial
- Feasibility, safety and efficacy of multi-dose vagus nerve stimulation in Parkinson's disease: a double-blind, randomised sham-controlled proof-of-concept study.Journal of neurology · 2025Trial
- Trial
- Midline Head Position for Preterm Infants in the First 72 h: A Pilot Randomised Control Trial.Journal of paediatrics and child health · 2025Trial
- intEgrating Smoking Cessation treatment As part of usual Psychological care for dEpression and anxiety (ESCAPE): A randomised and controlled, multi-centre, acceptability and feasibility trial with nested qualitative methods.Addiction (Abingdon, England) · 2025Trial
- A clinical trial evaluating feasibility and acceptability of a brain-computer interface for telerehabilitation in patients with stroke.Journal of neuroengineering and rehabilitation · 2025Trial
- Exploring the potential of a school brushing program using a connected brush in underserved areas: a feasibility cluster randomised trial.BMC oral health · 2025Trial
- Trial
19 more citing papers are in PubMed but not listed here.
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
7 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
objectivesTo review the consent, recruitment and retention rates for randomised controlled trials (RCTs) funded by the UK's National Institute for Health Research (NIHR) and published in the online NIHR Journals Library between January 1997 and December 2020.
designComprehensive review.
settingRCTs funded by the NIHR and published in the NIHR Journals Library. DATA EXTRACTION: Information relating to the trial characteristics, sample size, recruitment and retention. PRIMARY AND SECONDARY OUTCOME MEASURES: The primary outcome was the recruitment rate (number of participants recruited per centre per month). Secondary outcomes were the target sample size and whether it was achieved; consent rates (percentage of eligible participants who consented and were randomised) and retention rates (percentage of randomised participants retained and assessed with valid primary outcome data).
resultsThis review identified 388 individual RCTs from 379 reports in the NIHR Journals Library. The final recruitment target sample size was achieved in 63% (245/388) of the RCTs. The original recruitment target was revised in 30% (118/388) of trials (downwards in 67% (79/118)). The median recruitment rate (participants per centre per month) was found to be 0.95 (IQR: 0.42-2.60); the median consent rate was 72% (IQR: 50%-88%) and the median retention rate was estimated at 88% (IQR: 80%-97%).
conclusionsThere is considerable variation in the consent, recruitment and retention rates in publicly funded RCTs. Although the majority of (6 out of 10) trials in this review achieved their final target sample; 3 out of 10 trials revised their original target sample size (downwards in 7 out of 10 trials). Investigators should bear this in mind at the planning stage of their study and not be overly optimistic about their recruitment projections.
Indexed as
Identifiers
What OpenQuestion holds
Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.