Trial reportBMJ (Clinical research ed.)2021
Bah humbug! Association between sending Christmas cards to trial participants and trial retention: randomised study within a trial conducted simultaneously across eight host trials.
Trial report in BMJ (Clinical research ed.), 2021. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 13 papers, 2 of them syntheses that pooled it.
What it found
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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
13 citing papers in PubMed, 2 syntheses or guidelines pooled it.
- Recruitment and retention interventions in surgical and wound care trials: A systematic review.PloS one · 2023Pooled it
- Strategies to improve retention in randomised trials.The Cochrane database of systematic reviews · 2021Pooled it
- Trial
- Clinical and cost-effectiveness of percutaneous nephrolithotomy, flexible ureterorenoscopy and extracorporeal shockwave lithotripsy for lower pole stones: the PUrE RCTs.Health technology assessment (Winchester, England) · 2025Trial
- Laparoscopic cholecystectomy versus conservative management for adults with uncomplicated symptomatic gallstones: the C-GALL RCT.Health technology assessment (Winchester, England) · 2024Trial
- Bah humbug! Association between sending Christmas cards to trial participants and trial retention: randomised study within a trial conducted simultaneously across eight host trials.BMJ (Clinical research ed.) · 2021Trial
- A multilevel framework for recruitment and retention in implementation trials: An illustrative example.Clinical trials (London, England) · 2025Article
- Undertaking Studies Within A Trial to evaluate recruitment and retention strategies for randomised controlled trials: lessons learnt from the PROMETHEUS research programme.Health technology assessment (Winchester, England) · 2024Article
- How do trial teams plan for retention during the design stage of the trial? A scoping review.Trials · 2023Article
- Challenges and solutions to the implementation of studies within a trial: The experiences of the PROMETHEUS programme.Research methods in medicine & health sciences · 2023Article
- Study within a review (SWAR).Journal of evidence-based medicine · 2022Article
- Article
- The PROMoting the USE of SWATs (PROMETHEUS) programme: Lessons learnt and future developments for SWATs.Research methods in medicine & health sciences · 2022Article
Corrections and comments
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Authors and funding
10 authors.
Funding
Abstract
objectivesTo determine the effectiveness of sending Christmas cards to participants in randomised controlled trials to increase retention rate at follow-ups, and to explore the feasibility of doing a study within a trial (SWAT) across multiple host trials simultaneously.
designRandomised SWAT conducted simultaneously across eight host trials.
settingEight randomised controlled trials researching various areas including surgery and smoking cessation.
participants3223 trial participants who were still due at least one follow-up from their host randomised controlled trial.
interventionParticipants were randomised (1:1, separately by each host trial) to either received a Christmas card in mid-December 2019 or to not receive a card.
main outcome measureProportion of participants completing their next follow-up (retention rate) within their host randomised controlled trial.
results1469 participants (age 16-94 years; 70% (n=1033) female; 96% (813/847) white ethnicity) across the eight host randomised controlled trials were involved in the analysis (cut short owing to covid-19). No evidence was found of a difference in retention rate between the two arms for any of the host trials when analysed separately or when the results were combined (85.3% (639/749) for cards versus 85.4% (615/720) for no card; odds ratio 0.96, 95% confidence interval 0.71 to 1.29; P=0.77). No difference was observed when comparing just participants who were due a follow-up in the 30 days after receiving the card (odds ratio 0.96, 0.42 to 2.21). No evidence of a difference in time to complete the questionnaire was found (hazard ratio 1.01, 95% confidence interval 0.91 to 1.13; P=0.80). These results were robust to post hoc sensitivity analyses. The cost of this intervention was £0.76 (€0.91; $1.02) per participant, and it will have a carbon footprint of approximately 140 g CO
conclusionsSending Christmas cards to participants in randomised controlled trials does not increase retention. Undertaking a SWAT within multiple randomised controlled trials at the same time is, however, possible. This approach should be used more often to build an evidence base to support selection of recruitment and retention strategies. Although no evidence of a boost to retention was found, embedding a SWAT in multiple host trials simultaneously has been shown to be possible. STUDY REGISTRATION: SWAT repository https://www.qub.ac.uk/sites/TheNorthernIrelandNetworkforTrialsMethodologyResearch/FileStore/Filetoupload,846275,en.pdf#search=SWAT%2082.
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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.