BACKGROUND There is broad recognition of the importance of evidence in informing clinical decisions. When information from all studies included in a systematic review ("review") does not contribute to a meta-analysis, decision-makers can be frustrated. Our objectives were to use the field of eyes and vision as a case study and examine the extent to which authors of Cochrane reviews conducted meta-analyses for their review's pre-specified main outcome domain and the reasons that some otherwise eligible studies were not incorporated into meta-analyses. METHODS We examined all completed systematic reviews published by Cochrane Eyes and Vision, as of August 11, 2017. We extracted information about each review's outcomes and, using an algorithm, categorized one outcome as its "main" outcome. We calculated the percentage of included studies incorporated into meta-analyses for any outcome and for the main outcome. We examined reasons for non-inclusion of studies into the meta-analysis for the main outcome. RESULTS We identified 175 completed reviews, of which 125 reviews included two or more studies. Across these 125 reviews, the median proportions of studies incorporated into at least one meta-analysis for any outcome and for the main outcome were 74% (interquartile range [IQR] 0-100%) and 28% (IQR 0-71%), respectively. Fifty-one reviews (41%) could not conduct a meta-analysis for the main outcome, mostly because fewer than two included studies measured the outcome (21/51 reviews) or the specific measurements for the outcome were inconsistent (16/51 reviews). CONCLUSIONS Outcome choice during systematic reviews can lead to few eligible studies included in meta-analyses. Core outcome sets and improved reporting of outcomes can help solve some of these problems.

中文翻译：

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系统评价中的结果选择和定义导致荟萃分析中纳入的合格研究很少：案例研究。


背景人们广泛认识到证据对于临床决策的重要性。当系统评价（“评价”）中包含的所有研究的信息对荟萃分析没有贡献时，决策者可能会感到沮丧。我们的目标是使用眼睛和视力领域作为案例研究，并检查 Cochrane 综述的作者对其综述预先指定的主要结果领域进行荟萃分析的程度，以及一些其他符合条件的研究未纳入其中的原因。荟萃分析。方法 我们检查了截至 2017 年 8 月 11 日由 Cochrane Eyes and Vision 发表的所有已完成的系统评价。我们提取了每项评价结果的信息，并使用一种算法将一个结果分类为其“主要”结果。我们计算了纳入荟萃分析的任何结果和主要结果的纳入研究的百分比。我们研究了未将研究纳入主要结果荟萃分析的原因。结果 我们确定了 175 篇已完成的综述，其中 125 篇综述包含两项或更多研究。在这 125 篇综述中，纳入至少一项针对任何结局和主要结局的荟萃分析的研究中位数比例分别为 74%（四分位距 [IQR] 0-100%）和 28%（IQR 0-71%） ， 分别。 51 篇综述（41%）无法对主要结果进行荟萃分析，主要是因为少于两项纳入的研究测量了结果（21/51 篇综述）或结果的具体测量不一致（16/51 篇综述）。结论 系统评价期间的结果选择可能导致荟萃分析中纳入的合格研究很少。核心成果集和改进的成果报告可以帮助解决其中一些问题。