| Titre : | Impact of allocation concealment on conclusions drawn from meta-analyses of randomized trials. (2007) |
| Auteurs : | J. PILDAL ; ALTMAN (D.G.) : GBR. Centre for Statistics in Medicine. Oxford. ; P.C. GETZSCHE ; HILDEN (J.) : DNK. Department of Biostatistics. University of Copenhagen. ; A. HROBJARTSSON ; K.J. JORGENSEN ; Nordic Cochrane Centre. Rigshospitalet. DNK |
| Type de document : | Article |
| Dans : | International journal of epidemiology (vol. 36, n° 4, 2007) |
| Pagination : | 847-857 |
| Langues: | Anglais |
| Mots-clés : | Epidémiologie ; Essai double aveugle ; Homme |
| Résumé : | [BDSP. Notice produite par INIST-CNRS R0x2o5hi. Diffusion soumise à autorisation]. 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. |
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