Direction and impact of language bias in meta-analyses of controlled trials:: empirical study
Direction and impact of language bias in meta-analyses of controlled trials:: empirical study
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DOI：
10.1093/ije/31.1.115
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发表时间：
2002-02-01
影响因子：
7.7
通讯作者：
Egger, M
中科院分区：
文献类型：
--
作者：
Jüni, P;Holenstein, F;Egger, M
背景：从荟萃分析中排除用英语以外的语言报道的临床试验可能会引入偏差，并降低对治疗效果的综合估计的精确度。我们考察了非英语语言发表的试验对已发表的Meta分析的综合估计和结论的影响。方法我们在期刊和Cochrane系统综述数据库中搜索至少5项具有二项结果的试验的Meta分析，这些试验基于全面的文献检索而不受语言限制。结果我们确定了303项荟萃分析：159项(52.4%)采用了全面的文献检索，其中50项包括485项英语试验和115项非英语语言试验。非英语语言试验的参与者较少(中位数88人比116人，P=0.006)，并且更有可能在P<；0.05时产生显著结果(41.7%比31.3%，P=0.033)。非英语语言试验的方法学质量往往低于以英语发表的试验。对治疗效果的估计在非英语试验中比在英语试验中更有益，平均为16%(95%可信区间：3-26%)。在29项(58.0%)Meta分析中，排除非英语语言试验后效果估计的变化不到5%。在剩余的Meta分析中，排除非英语语言试验后，5例(10.0%)获益较多，16例(32.0%)获益较少。结论本次回顾性分析表明，排除非英语语言发表的试验总体上对汇总疗效估计影响不大。然而，对于个别的系统评价来说，非英语语言试验的重要性很难预测。需要进行全面的文献搜索，然后仔细评估试验质量，以评估所有相关试验的贡献，而不受出版语言的影响。
Background Excluding clinical trials reported in languages other than English from meta-analyses may introduce bias and reduce the precision of combined estimates of treatment effects. We examined the influence of trials published in languages other than English on combined estimates and conclusions of published meta-analyses.Methods We searched journals and the Cochrane Database of Systematic Reviews for meta-analyses of at least five trials with binary outcomes that were based on comprehensive literature searches without language restrictions. We compared estimates of treatment effects from trials published in languages other than English to those from trials published in English, and assessed the impact of restricting meta-analyses to trials published in English.Results We identified 303 meta-analyses: 159 (52.4%) employed comprehensive literature searches of which 50 included 485 English and 115 non-English language trials. Non-English language trials included fewer participants (median 88 versus 116, P = 0.006) and were more likely to produce significant results at P < 0.05 (41.7% versus 31.3%, P = 0.033). The methodological quality of non-English language trials tended to be lower than that of trials published in English. Estimates of treatment effects were on average 16% (95% CI: 3-26%) more beneficial in non-English-language trials than in English-language trials. In 29 (58.0%) meta-analyses the change in effect estimates after exclusion of non-English language trials was less than 5%. In the remaining meta-analyses, 5 (10.0%) showed more benefit and 16 (32.0%) less benefit after exclusion of non-English language trials.Conclusions This retrospective analysis suggests that excluding trials published in languages other than English has generally little effect on summary treatment effect estimates. The importance of non-English language trials is, however, difficult to predict for individual systematic reviews. Comprehensive literature searches followed by a careful assessment of trial quality are required to assess the contribution of all relevant trials, independent of language of publication.