Souza João P, Pileggi Cynthia, Cecatti José G
Department of Obstetrics and Gynecology, School of Medical Sciences, University of Campinas, Brazil.
Reprod Health. 2007 Apr 16;4:3. doi: 10.1186/1742-4755-4-3.
Despite efforts to assure high methodological standards, systematic reviews may be affected by publication bias. The objective of this study was to evaluate the occurrence of publication bias in a collection of high quality systematic reviews on reproductive health.
Systematic reviews included in the Reproductive Health Library (RHL), issue No 9, were assessed. Funnel plot was used to assess meta-analyses containing 10 or more trials reporting a binary outcome. A funnel plot, the estimated number of missing studies and the adjusted combined effect size were obtained using the "trim and fill method". Meta-analyses results that were not considered to be robust due to a possible publication bias were submitted to a more detailed assessment.
A total of 21 systematic reviews were assessed. The number of trials comprising each one ranged from 10 to 83 (median = 13), totaling 379 trials, whose results have been summarized. None of the reviews had reported any evaluation of publication bias or funnel plot asymmetry. Some degree of asymmetry in funnel plots was observed in 18 of the 21 meta-analyses evaluated (85.7%), with the estimated number of missing studies ranging from 1 to 18 (median = 3). Only for three meta-analyses, the conclusion could not be considered robust due to a possible publication bias.
Asymmetry is a frequent finding in funnel plots of meta-analyses in reproductive health, but according to the present evaluation, less than 15% of meta-analyses report conclusions that would not be considered robust. Publication bias and other sources of asymmetry in funnel plots should be systematically addressed by reproductive health meta-analysts. Next amendments in Cochrane systematic reviews should include this type of evaluation. Further studies regarding the evolution of effect size and publication bias over time in systematic reviews in reproductive health are needed.
尽管努力确保高方法学标准，但系统评价可能受到发表偏倚的影响。本研究的目的是评估一组关于生殖健康的高质量系统评价中发表偏倚的发生情况。
对《生殖健康图书馆》（RHL）第9期纳入的系统评价进行评估。漏斗图用于评估包含10项或更多报告二元结局试验的Meta分析。使用“修剪和填充法”获得漏斗图、缺失研究的估计数量和调整后的合并效应量。由于可能存在发表偏倚而被认为不稳健的Meta分析结果进行更详细的评估。
共评估了21项系统评价。每项系统评价所包含的试验数量从10项到83项不等（中位数=13），总计379项试验，其结果已被总结。没有一项评价报告对发表偏倚或漏斗图不对称性进行任何评估。在评估的21项Meta分析中有18项（85.7%）观察到漏斗图存在一定程度的不对称，缺失研究的估计数量从1项到18项不等（中位数=3）。仅3项Meta分析由于可能存在发表偏倚，其结论不被认为是稳健的。
不对称是生殖健康Meta分析漏斗图中的常见发现，但根据目前的评估，不到15%的Meta分析报告的结论不被认为是稳健的。生殖健康Meta分析人员应系统地解决发表偏倚和漏斗图中其他不对称来源的问题。Cochrane系统评价的下一次修订应包括此类评估。需要进一步研究生殖健康系统评价中效应量和发表偏倚随时间的演变情况。
