SynthesisBMJ (Clinical research ed.)2009
The effects of excluding patients from the analysis in randomised controlled trials: meta-epidemiological study.
Synthesis in BMJ (Clinical research ed.), 2009. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 105 papers, 44 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
105 citing papers in PubMed, 44 syntheses or guidelines pooled it, 243 citations in OpenAlex.
- Effectiveness of exercise therapy for osteoarthritis: an overview of systematic reviews and randomised controlled trials.RMD open · 2026Pooled it
- Comparative assessment of surgical outcomes and cost-efficiency between orthopedic surgeons and neurosurgeons in degenerative lumbar spine surgery: a systematic review with pairwise and proportional meta-analysis.Neurosurgical review · 2025Pooled it
- Pooled it
- Eligible Infants Included in Neonatal Clinical Trials and Reasons for Noninclusion: A Systematic Review.JAMA network open · 2024Pooled it
- A systematic review and meta-analysis of treatments for rapid cycling bipolar disorder.Acta psychiatrica Scandinavica · 2022Pooled it
- The effectiveness of different electrical nerve stimulation protocols for treating adults with non-neurogenic overactive bladder: a systematic review and meta-analysis.International urogynecology journal · 2022Pooled it
- Withdrawal reasons of randomized controlled trials on type 2 diabetes: a systematic review.Daru : journal of Faculty of Pharmacy, Tehran University of Medical Sciences · 2021Pooled it
- Wound cleansing for treating venous leg ulcers.The Cochrane database of systematic reviews · 2021Pooled it
- Mechanically assisted walking training for walking, participation, and quality of life in children with cerebral palsy.The Cochrane database of systematic reviews · 2020Pooled it
- Effects of isoflavone interventions on bone mineral density in postmenopausal women: a systematic review and meta-analysis of randomized controlled trials.Osteoporosis international : a journal established as result of cooperation between the European Foundation for Osteoporosis and the National Osteoporosis Foundation of the USA · 2020Pooled it
- Psychological therapies for the management of chronic pain (excluding headache) in adults.The Cochrane database of systematic reviews · 2020Pooled it
- Bias and Loss to Follow-Up in Cardiovascular Randomized Trials: A Systematic Review.Journal of the American Heart Association · 2020Pooled it
- Constraint-induced movement therapy in children with unilateral cerebral palsy.The Cochrane database of systematic reviews · 2019Pooled it
- The effectiveness of virtual reality based interventions for symptoms of anxiety and depression: A meta-analysis.Scientific reports · 2018Pooled it
- Interventions for treating persistent pain in survivors of torture.The Cochrane database of systematic reviews · 2017Pooled it
- Exercise interventions for cerebral palsy.The Cochrane database of systematic reviews · 2017Pooled it
- Intra-Articular Therapies in the Treatment of Hand Osteoarthritis: A Systematic Literature Review.Drugs & aging · 2016Pooled it
- Empirical Evidence of Study Design Biases in Randomized Trials: Systematic Review of Meta-Epidemiological Studies.PloS one · 2016Pooled it
- Where Have All the Rodents Gone? The Effects of Attrition in Experimental Research on Cancer and Stroke.PLoS biology · 2016Pooled it
- Effectiveness of Manual Therapy and Therapeutic Exercise for Temporomandibular Disorders: Systematic Review and Meta-Analysis.Physical therapy · 2016Pooled it
45 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
8 authors at 5 institutions in 4 countries.
Funding
No grant is acknowledged in the PubMed record.
Abstract
objectiveTo examine whether excluding patients from the analysis of randomised trials are associated with biased estimates of treatment effects and higher heterogeneity between trials.
designMeta-epidemiological study based on a collection of meta-analyses of randomised trials. DATA SOURCES: 14 meta-analyses including 167 trials that compared therapeutic interventions with placebo or non-intervention control in patients with osteoarthritis of the hip or knee and used patient reported pain as an outcome.
methodsEffect sizes were calculated from differences in means of pain intensity between groups at the end of follow-up, divided by the pooled standard deviation. Trials were combined by using random effects meta-analysis. Estimates of treatment effects were compared between trials with and trials without exclusions from the analysis, and the impact of restricting meta-analyses to trials without exclusions was assessed.
results39 trials (23%) had included all patients in the analysis. In 128 trials (77%) some patients were excluded from the analysis. Effect sizes from trials with exclusions tended to be more beneficial than those from trials without exclusions (difference -0.13, 95% confidence interval -0.29 to 0.04). However, estimates of bias between individual meta-analyses varied considerably (tau(2)=0.07). Tests of interaction between exclusions from the analysis and estimates of treatment effects were positive in five meta-analyses. Stratified analyses indicated that differences in effect sizes between trials with and trials without exclusions were more pronounced in meta-analyses with high between trial heterogeneity, in meta-analyses with large estimated treatment benefits, and in meta-analyses of complementary medicine. Restriction of meta-analyses to trials without exclusions resulted in smaller estimated treatment benefits, larger P values, and considerable decreases in between trial heterogeneity.
conclusionExcluding patients from the analysis in randomised trials often results in biased estimates of treatment effects, but the extent and direction of bias is unpredictable. Results from intention to treat analyses should always be described in reports of randomised trials. In systematic reviews, the influence of exclusions from the analysis on estimated treatment effects should routinely be assessed.
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.