ArticleBMC medical research methodology2016
Mechanisms and direction of allocation bias in randomised clinical trials.
Article in BMC medical research methodology, 2016. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 11 papers, 5 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.
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Who cites it
11 citing papers in PubMed, 5 syntheses or guidelines pooled it.
- Prehabilitation programs for individuals with cancer: a systematic review of randomized-controlled trials.Systematic reviews · 2023Pooled it
- A systematic review and meta-analysis of the effects of Hibiscus sabdariffa on blood pressure and cardiometabolic markers.Nutrition reviews · 2022Pooled it
- Corticosteroid injection or dry needling for musculoskeletal pain and disability? A systematic review and GRADE evidence synthesis.Chiropractic & manual therapies · 2021Pooled it
- Pooled it
- Clowning in children undergoing potentially anxiety-provoking procedures: a systematic review and meta-analysis.Systematic reviews · 2019Pooled it
- Rapid, effective, and affordable randomisation for emergency neonatal research in a low-resource setting: a feasibility randomised controlled trial.BMC medical research methodology · 2026Trial
- Daily consumption of γ-oryzanol-fortified canola oil, compared with unfortified canola and sunflower oils, resulted in a better improvement of certain cardiometabolic biomarkers of adult subjects with type 2 diabetes: a randomized controlled clinical trial.European journal of medical research · 2023Trial
- Mapping the Nitric Oxide Axis in IVF: Genotype Associations in Antagonist Cycles.International journal of molecular sciences · 2025Article
- A Systematic Review Comparing Experimental Design of Animal and Human Methotrexate Efficacy Studies for Rheumatoid Arthritis: Lessons for the Translational Value of Animal Studies.Animals : an open access journal from MDPI · 2020Review
- Bias in clinical trials into the effects of complementary and alternative medicine therapies on hemodialysis patients.Journal of family medicine and primary care · 2019Review
- Review
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
3 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
backgroundSelective allocation of patients into the compared groups of a randomised trial may cause allocation bias, but the mechanisms behind the bias and its directionality are incompletely understood. We therefore analysed the mechanisms and directionality of allocation bias in randomised clinical trials.
methodsTwo systematic reviews and a theoretical analysis. We conducted one systematic review of empirical studies of motives/methods for deciphering patient allocation sequences; and another review of methods publications commenting on allocation bias. We theoretically analysed the mechanisms of allocation bias and hypothesised which main factors predicts its direction.
resultsThree empirical studies addressed motives/methods for deciphering allocation sequences. Main motives included ensuring best care for patients and ensuring best outcome for the trial. Main methods included various manipulations with randomisation envelopes. Out of 57 methods publications 11 (19 %) mentioned explicitly that allocation bias can go in either direction. We hypothesised that the direction of allocation bias is mainly decided by the interaction between the patient allocators' motives and treatment preference.
conclusionInadequate allocation concealment may exaggerate treatment effects in some trials while underestimate effects in others. Our hypothesis provides a theoretical overview of the main factors responsible for the direction of allocation bias.
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