University of Maastricht, School for Public Health and Primary Care, Maastricht, The Netherlands ; Children's Hospital, University of Cologne, Cologne, Germany.
University of Birmingham, Department of Public Health, Epidemiology & Biostatistics, Birmingham, United Kingdom.
PLoS One. 2013 Dec 26;8(12):e85035. doi: 10.1371/journal.pone.0085035. eCollection 2013.
A systematic review may evaluate different aspects of a health care intervention. To accommodate the evaluation of various research questions, the inclusion of more than one study design may be necessary. One aim of this study is to find and describe articles on methodological issues concerning the incorporation of multiple types of study designs in systematic reviews on health care interventions. Another aim is to evaluate methods studies that have assessed whether reported effects differ by study types.
We searched PubMed, the Cochrane Database of Systematic Reviews, and the Cochrane Methodology Register on 31 March 2012 and identified 42 articles that reported on the integration of single or multiple study designs in systematic reviews. We summarized the contents of the articles qualitatively and assessed theoretical and empirical evidence. We found that many examples of reviews incorporating multiple types of studies exist and that every study design can serve a specific purpose. The clinical questions of a systematic review determine the types of design that are necessary or sufficient to provide the best possible answers. In a second independent search, we identified 49 studies, 31 systematic reviews and 18 trials that compared the effect sizes between randomized and nonrandomized controlled trials, which were statistically different in 35%, and not different in 53%. Twelve percent of studies reported both, different and non-different effect sizes.
Different study designs addressing the same question yielded varying results, with differences in about half of all examples. The risk of presenting uncertain results without knowing for sure the direction and magnitude of the effect holds true for both nonrandomized and randomized controlled trials. The integration of multiple study designs in systematic reviews is required if patients should be informed on the many facets of patient relevant issues of health care interventions.
系统评价可以评估医疗干预的不同方面。为了适应各种研究问题的评估，可能需要纳入多种研究设计。本研究的目的之一是查找和描述有关系统评价中纳入多种研究设计的方法学问题的文章。另一个目的是评估评估报告效果是否因研究类型而异的方法研究。
我们于 2012 年 3 月 31 日检索了 PubMed、Cochrane 系统评价数据库和 Cochrane 方法学注册库，共识别出 42 篇报道系统评价中整合单一或多种研究设计的文章。我们对文章内容进行了定性总结，并评估了理论和经验证据。我们发现，存在许多纳入多种类型研究的综述实例，并且每种研究设计都可以服务于特定目的。系统评价的临床问题决定了提供最佳答案所需的设计类型。在第二个独立搜索中，我们确定了 49 项研究，其中 31 项系统评价和 18 项试验比较了随机对照试验和非随机对照试验的效应大小，其中 35%的效应大小存在统计学差异，53%的效应大小无差异。12%的研究报告了不同和相同的效应大小。
针对同一问题的不同研究设计产生了不同的结果，其中约一半的结果存在差异。对于不确定的结果，不知道效果的方向和大小，这种情况既适用于非随机对照试验，也适用于随机对照试验。如果要向患者提供有关医疗干预患者相关问题的许多方面的信息，则需要在系统评价中整合多种研究设计。
