IRCCS Fondazione Don Carlo Gnocchi, Milan, Italy.
Department of Clinical Science and Translational Medicine, Faculty of Medicine and Surgery, University of Rome Tor Vergata, Rome, Italy.
BMC Med Res Methodol. 2023 Oct 21;23(1):245. doi: 10.1186/s12874-023-02064-7.
Systematic reviews of randomized controlled trials are the best evidence for informing on intervention effectiveness. Their results, however, can be biased due to omitted evidence in the quantitative analyses. We aimed to assess the proportion of randomized controlled trials omitted from meta-analyses in the rehabilitation field and explore related reasons.
This is a cross-sectional meta-research study. For each systematic review included in a published selected sample in the rehabilitation field, we identified an index meta-analysis on the primary outcome and the main comparison. We then looked at all the studies considered eligible for the chosen comparison in the systematic review and identified those trials that have been omitted (i.e., not included) from each index meta-analysis. Reasons for omission were collected based on an eight-reason classification. We used descriptive statistics to describe the proportion of omitted trials overall and according to each reason.
Starting from a cohort of 827 systematic reviews, 131 index meta-analyses comprising a total of 1761 eligible trials were selected. Only 16 index meta-analyses included all eligible studies while 15 omitted studies without providing references. From the remaining 100 index meta-analyses, 717 trials (40,7%) were omitted overall. Specific reasons for omission were: "unable to distinguish between selective reporting and inadequate planning" (39,3%, N = 282), "inadequate planning" (17%, N = 122), "justified to be not included" (15,1%, N = 108), "incomplete reporting" (8,4%, N = 60), "selective reporting" (3,3%, N = 24) and other situations (e.g., outcome present but no motivation for omission) (5,2%, N = 37). The 11,7% (N = 84) of omitted trials were not assessed due to non-English language or full text not available.
Almost half of the eligible trials were omitted from their index meta-analyses. Better reporting, protocol registration, definition and adoption of core outcome sets are needed to prevent omission of evidence in systematic reviews.
系统评价随机对照试验是为干预效果提供信息的最佳证据。然而，由于在定量分析中遗漏了证据，其结果可能存在偏倚。我们旨在评估康复领域中被纳入荟萃分析的随机对照试验的比例，并探讨相关原因。
这是一项横断面的元研究。对于发表的康复领域选定样本中包含的每一项系统评价，我们确定了一项针对主要结局和主要比较的指标荟萃分析。然后，我们查看了系统评价中被认为符合选择比较标准的所有研究，并确定了从每项指标荟萃分析中被遗漏（即未纳入）的试验。根据八项分类收集遗漏原因。我们使用描述性统计方法来描述总体上和根据每个原因遗漏的试验比例。
从 827 项系统评价中，选择了 131 项指标荟萃分析，其中包含 1761 项符合条件的试验。只有 16 项指标荟萃分析纳入了所有符合条件的研究，而 15 项未提供参考文献的研究被遗漏。在其余 100 项指标荟萃分析中，共有 717 项试验（40.7%）被遗漏。遗漏的具体原因包括：“无法区分选择性报告和计划不足”（39.3%，N=282）、“计划不足”（17%，N=122）、“有理由不包括”（15.1%，N=108）、“报告不完整”（8.4%，N=60）、“选择性报告”（3.3%，N=24）和其他情况（例如，结局存在但没有遗漏的动机）（5.2%，N=37）。由于语言不是英语或无法获取全文，11.7%（N=84）的遗漏试验未被评估。
近一半的合格试验被从其指标荟萃分析中遗漏。需要更好的报告、方案注册、核心结局集的定义和采用，以防止系统评价中遗漏证据。
