Vaitkus Paul T, Brar Charanjit
Cardiology Division, M/C 715, University of Illinois at Chicago, Chicago, IL 60612, USA.
Am Heart J. 2007 Feb;153(2):275-80. doi: 10.1016/j.ahj.2006.09.014.
The use of N-acetylcysteine for the prevention of contrast-induced nephropathy has been the subject of numerous clinical trials and meta-analyses. We sought to examine the possibility of a publication bias and whether meta-analyses have magnified any potential publication bias.
We performed a Medline search and a manual search to identify published manuscripts. We also manually searched contemporaneous major cardiology scientific meetings to identify abstracts. We included only randomized controlled clinical trials. We pooled the results of abstracts and manuscripts separately and combined, calculating an odds ratio (OR). We analyzed meta-analyses according to the proportions of manuscripts and abstracts that they included and compared their calculated ORs to the OR of all available contemporaneous data. Our analysis spanned the time from the publication of the first manuscript on this topic through June 2006.
Throughout the study period, the published manuscripts presented a treatment-effect estimate that was more optimistic than that found in unpublished abstracts. There was a temporal trend in that the estimate of treatment effect was greatest with early publications, which diminished as additional data became available. The profile of the journal (as assessed by impact factor) in which a manuscript was published was not related to the quality of the manuscript. However, studies reaching a positive conclusion were published in journals with higher impact factors compared with studies reaching negative conclusions. Meta-analyses included a substantially greater proportion of published manuscripts versus unpublished abstracts and provided more optimistic assessments of treatment effect than would have been derived had all available data been assessed.
There was a significant publication bias that persisted throughout the life cycle of this clinical question. The bias was further amplified by meta-analyses.
使用N-乙酰半胱氨酸预防造影剂肾病一直是众多临床试验和荟萃分析的主题。我们试图研究发表偏倚的可能性，以及荟萃分析是否放大了任何潜在的发表偏倚。
我们进行了Medline检索和手工检索以识别已发表的手稿。我们还对手工检索同期的主要心脏病学科学会议以识别摘要。我们仅纳入随机对照临床试验。我们分别汇总摘要和手稿的结果并合并，计算比值比（OR）。我们根据所纳入的手稿和摘要的比例分析荟萃分析，并将其计算的OR与所有同期可用数据的OR进行比较。我们的分析涵盖了从关于该主题的第一篇手稿发表到2006年6月的时间段。
在整个研究期间，已发表的手稿呈现出比未发表摘要中更乐观的治疗效果估计。存在一种时间趋势，即早期发表的治疗效果估计最大，随着更多数据的出现而减小。发表手稿的期刊的概况（通过影响因子评估）与手稿质量无关。然而，得出阳性结论的研究发表在影响因子较高的期刊上，而得出阴性结论的研究则不然。荟萃分析纳入的已发表手稿比例远高于未发表摘要，并且与评估所有可用数据相比，对治疗效果提供了更乐观的评估。
在这个临床问题的整个生命周期中存在显著的发表偏倚。荟萃分析进一步放大了这种偏倚。
