%0 Journal Article %1 Pildal2007 %A Pildal, J %A Hróbjartsson, A %A Jørgensen, K J %A Hilden, J %A Altman, D G %A Gøtzsche, P C %D 2007 %J International journal of epidemiology %K Bias(Epidemiology) DataInterpretation Double-BlindMethod Humans Meta-AnalysisasTopic SensitivityandSpecificity Single-BlindMethod Statistical TreatmentOutcome RCT %N 4 %P 847-57 %R 10.1093/ije/dym087 %T Impact of allocation concealment on conclusions drawn from meta-analyses of randomized trials. %U http://www.ncbi.nlm.nih.gov/pubmed/17517809 %V 36 %X BACKGROUND: Randomized trials without reported adequate allocation concealment have been shown to overestimate the benefit of experimental interventions. We investigated the robustness of conclusions drawn from meta-analyses to exclusion of such trials. MATERIAL: Random sample of 38 reviews from The Cochrane Library 2003, issue 2 and 32 other reviews from PubMed accessed in 2002. Eligible reviews presented a binary effect estimate from a meta-analysis of randomized controlled trials as the first statistically significant result that supported a conclusion in favour of one of the interventions. METHODS: We assessed the methods sections of the trials in each included meta-analysis for adequacy of allocation concealment. We replicated each meta-analysis using the authors' methods but included only trials that had adequate allocation concealment. Conclusions were defined as not supported if our result was not statistically significant. RESULTS: Thirty-four of the 70 meta-analyses contained a mixture of trials with unclear or inadequate concealment as well as trials with adequate allocation concealment. Four meta-analyses only contained trials with adequate concealment, and 32, only trials with unclear or inadequate concealment. When only trials with adequate concealment were included, 48 of 70 conclusions (69%; 95% confidence interval: 56-79%) lost support. The loss of support mainly reflected loss of power (the total number of patients was reduced by 49%) but also a shift in the point estimate towards a less beneficial effect. CONCLUSION: Two-thirds of conclusions in favour of one of the interventions were no longer supported if only trials with adequate allocation concealment were included. %@ 0300-5771

@article{Pildal2007, abstract = {BACKGROUND: Randomized trials without reported adequate allocation concealment have been shown to overestimate the benefit of experimental interventions. We investigated the robustness of conclusions drawn from meta-analyses to exclusion of such trials. MATERIAL: Random sample of 38 reviews from The Cochrane Library 2003, issue 2 and 32 other reviews from PubMed accessed in 2002. Eligible reviews presented a binary effect estimate from a meta-analysis of randomized controlled trials as the first statistically significant result that supported a conclusion in favour of one of the interventions. METHODS: We assessed the methods sections of the trials in each included meta-analysis for adequacy of allocation concealment. We replicated each meta-analysis using the authors' methods but included only trials that had adequate allocation concealment. Conclusions were defined as not supported if our result was not statistically significant. RESULTS: Thirty-four of the 70 meta-analyses contained a mixture of trials with unclear or inadequate concealment as well as trials with adequate allocation concealment. Four meta-analyses only contained trials with adequate concealment, and 32, only trials with unclear or inadequate concealment. When only trials with adequate concealment were included, 48 of 70 conclusions (69%; 95% confidence interval: 56-79%) lost support. The loss of support mainly reflected loss of power (the total number of patients was reduced by 49%) but also a shift in the point estimate towards a less beneficial effect. CONCLUSION: Two-thirds of conclusions in favour of one of the interventions were no longer supported if only trials with adequate allocation concealment were included.}, added-at = {2023-02-03T11:44:35.000+0100}, author = {Pildal, J and Hróbjartsson, A and Jørgensen, K J and Hilden, J and Altman, D G and Gøtzsche, P C}, biburl = {https://www.bibsonomy.org/bibtex/222697187e815c90e4d776cefc324c721/jepcastel}, city = {The Nordic Cochrane Centre, Rigshospitalet, DK. jp@cochrance.dk}, doi = {10.1093/ije/dym087}, interhash = {8399a088cd12febadb5ce63207f77a0d}, intrahash = {22697187e815c90e4d776cefc324c721}, isbn = {0300-5771}, issn = {0300-5771}, journal = {International journal of epidemiology}, keywords = {Bias(Epidemiology) DataInterpretation Double-BlindMethod Humans Meta-AnalysisasTopic SensitivityandSpecificity Single-BlindMethod Statistical TreatmentOutcome RCT}, month = {8}, note = {5316<m:linebreak></m:linebreak>LR: 20080616; JID: 7802871; EIN: Int J Epidemiol. 2008 Apr;37(2):422; 2007/05/21 [aheadofprint]; ppublish;<m:linebreak></m:linebreak>Metaanàlisi}, number = 4, pages = {847-57}, pmid = {17517809}, timestamp = {2023-05-04T09:00:45.000+0200}, title = {Impact of allocation concealment on conclusions drawn from meta-analyses of randomized trials.}, url = {http://www.ncbi.nlm.nih.gov/pubmed/17517809}, volume = 36, year = 2007 }