ArticleTrials2015
Specifying the target difference in the primary outcome for a randomised controlled trial: guidance for researchers.
Article in Trials, 2015. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 37 papers, 5 of them syntheses that pooled it.
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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.
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Who cites it
37 citing papers in PubMed, 5 syntheses or guidelines pooled it.
- Colchicine for the primary prevention of cardiovascular events.The Cochrane database of systematic reviews · 2025Pooled it
- Structure-Function Relationships in the Rodent Streptozotocin-Induced Model for Diabetic Retinopathy: A Systematic Review.Journal of ocular pharmacology and therapeutics : the official journal of the Association for Ocular Pharmacology and Therapeutics · 2022Pooled it
- Preventive Treatments for Psychosis: Umbrella Review (Just the Evidence).Frontiers in psychiatry · 2019Pooled it
- Guideline
- Clinical significance in pediatric oncology randomized controlled treatment trials: a systematic review.Trials · 2018Pooled it
- A Multicentered Randomized Controlled Trial Comparing the Effectiveness of Pain Treatment Communication Tools in Emergency Department Patients With Back or Kidney Stone Pain.American journal of public health · 2022Trial
- Internet delivery of intensive speech and language therapy for children with cerebral palsy: a pilot randomised controlled trial.BMJ open · 2019Trial
- Ethical implications of excessive cluster sizes in cluster randomised trials.BMJ quality & safety · 2018Trial
- How should minimally important change scores for the Patient-Oriented Eczema Measure be interpreted? A validation using varied methods.The British journal of dermatology · 2018Trial
- An RCT study comparing the clinical and radiological outcomes with the use of PLIF or TLIF after instrumented reduction in adult isthmic spondylolisthesis.European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society · 2016Trial
- Trial
- Refined trial sequential analysis for meta-analyses with few studies.Journal of the Royal Statistical Society. Series C, Applied statistics · 2026Article
- Article
- SPIRIT 2025 explanation and elaboration: updated guideline for protocols of randomised trials.BMJ (Clinical research ed.) · 2025Article
- Reporting and communication of sample size calculations in adaptive clinical trials: a review of trial protocols and grant applications.BMC medical research methodology · 2024Review
- Using the benefit-harm trade-off method to determine the smallest worthwhile effect of intensive motor training on strength for people with spinal cord injury.Spinal cord · 2024Article
- Protocol for a randomised controlled feasibility study examining the efficacy of brief cognitive therapy for the treatment of panic disorder in adolescents (PANDA).Pilot and feasibility studies · 2022Article
- A systematic review investigating the use of microbiology outcome measures in randomized controlled trials evaluating antimicrobial stewardship interventions published between 2011 and 2021.JAC-antimicrobial resistance · 2022Review
- Patient-reported outcomes and target effect sizes in pragmatic randomized trials in ClinicalTrials.gov: A cross-sectional analysis.PLoS medicine · 2022Review
- Living Systematic Reviews.Methods in molecular biology (Clifton, N.J.) · 2022Article
Corrections and comments
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Authors and funding
13 authors.
Funding
Abstract
backgroundCentral to the design of a randomised controlled trial is the calculation of the number of participants needed. This is typically achieved by specifying a target difference and calculating the corresponding sample size, which provides reassurance that the trial will have the required statistical power (at the planned statistical significance level) to identify whether a difference of a particular magnitude exists. Beyond pure statistical or scientific concerns, it is ethically imperative that an appropriate number of participants should be recruited. Despite the critical role of the target difference for the primary outcome in the design of randomised controlled trials, its determination has received surprisingly little attention. This article provides guidance on the specification of the target difference for the primary outcome in a sample size calculation for a two parallel group randomised controlled trial with a superiority question.
methodsThis work was part of the DELTA (Difference ELicitation in TriAls) project. Draft guidance was developed by the project steering and advisory groups utilising the results of the systematic review and surveys. Findings were circulated and presented to members of the combined group at a face-to-face meeting, along with a proposed outline of the guidance document structure, containing recommendations and reporting items for a trial protocol and report. The guidance and was subsequently drafted and circulated for further comment before finalisation.
resultsGuidance on specification of a target difference in the primary outcome for a two group parallel randomised controlled trial was produced. Additionally, a list of reporting items for protocols and trial reports was generated.
conclusionsSpecification of the target difference for the primary outcome is a key component of a randomized controlled trial sample size calculation. There is a need for better justification of the target difference and reporting of its specification.
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