Egger M
Department of Social Medicine, University of Bristol.
Schweiz Med Wochenschr. 1998 Nov 28;128(48):1893-901.
Critical review and statistical synthesis of the best evidence that is available on the benefits and risks of medical interventions is an important component of evidence-based medicine. There is, however, controversy regarding the merits and perils of this approach. In this article the potential and limitations of meta-analysis are illustrated and the problems of applying meta-analytical results to the individual patient are discussed. Whereas the classical narrative review article often reflects the personal opinion of the author, systematic reviews are characterized by clearly defined objectives and reproducible methods. If appropriate and feasible, individual studies are combined in a meta-analysis which will lead to enhanced precision of effect estimates. The potential of meta-analysis is illustrated by considering a patient who suffered a myocardial infarction in 1981. After consulting a misleading narrative review, this patient was discharged without beta-blockade for secondary prevention. Meta-analyses are, however, also liable to bias. For example, a meta-analysis of trials of magnesium infusions in acute myocardial infarction showed a substantial reduction in mortality. The beneficial effect of magnesium was not confirmed in the large ISIS-4 trial published in 1995. The occurrence of misleading meta-analyses is not surprising considering the selective publication of "positive" findings and the often inadequate quality of component studies. Misleading meta-analyses may also result from the inappropriate combination of heterogeneous studies. Every patient is unique regarding the exact localization and severity of the lesion, preexisting abilities, co-morbidity, social environment, personality and emotional response. The appropriate application of meta-analytic findings to the individual patient is difficult. It requires consideration of both quantitative and qualitative approaches to decision-making. Emphatic integration of these approaches characterizes the experienced, scientifically and socially competent physician.
对现有医学干预措施的益处和风险的最佳证据进行批判性综述和统计综合，是循证医学的一个重要组成部分。然而，对于这种方法的优点和风险存在争议。在本文中，阐述了荟萃分析的潜力和局限性，并讨论了将荟萃分析结果应用于个体患者的问题。传统的叙述性综述文章往往反映作者的个人观点，而系统综述的特点是目标明确且方法可重复。如果合适且可行，将个体研究合并进行荟萃分析，这将提高效应估计的精确度。通过考虑一名在1981年发生心肌梗死的患者来说明荟萃分析的潜力。在查阅了一篇有误导性的叙述性综述后，该患者在未接受β受体阻滞剂二级预防的情况下出院。然而，荟萃分析也容易出现偏差。例如，一项关于急性心肌梗死中静脉输注镁的试验的荟萃分析显示死亡率大幅降低。1995年发表的大型ISIS - 4试验并未证实镁的有益效果。考虑到“阳性”结果的选择性发表以及组成研究的质量往往不足，出现误导性的荟萃分析并不奇怪。误导性的荟萃分析也可能源于对异质性研究的不恰当合并。每个患者在病变的确切位置和严重程度、既往能力、合并症、社会环境、个性和情绪反应方面都是独特的。将荟萃分析结果适当地应用于个体患者是困难的。这需要同时考虑定量和定性的决策方法。这些方法的有力整合是经验丰富、具备科学和社会能力的医生的特征。
