Friedrich Jan O, Adhikari Neill K J, Beyene Joseph
Interdepartmental Division of Critical Care, University of Toronto, Toronto, Canada.
BMC Med Res Methodol. 2007 Jan 23;7:5. doi: 10.1186/1471-2288-7-5.
Meta-analysis handles randomized trials with no outcome events in both treatment and control arms inconsistently, including them when risk difference (RD) is the effect measure but excluding them when relative risk (RR) or odds ratio (OR) are used. This study examined the influence of such trials on pooled treatment effects.
Analysis with and without zero total event trials of three illustrative published meta-analyses with a range of proportions of zero total event trials, treatment effects, and heterogeneity using inverse variance weighting and random effects that incorporates between-study heterogeneity.
Including zero total event trials in meta-analyses moves the pooled estimate of treatment effect closer to nil, decreases its confidence interval and decreases between-study heterogeneity. For RR and OR, inclusion of such trials causes small changes, even when they comprise the large majority of included trials. For RD, the changes are more substantial, and in extreme cases can eliminate a statistically significant effect estimate.
To include all relevant data regardless of effect measure chosen, reviewers should also include zero total event trials when calculating pooled estimates using OR and RR.
荟萃分析在处理治疗组和对照组均无结局事件的随机试验时存在不一致性，当效应量采用风险差（RD）时将其纳入，但当使用相对风险（RR）或比值比（OR）时将其排除。本研究考察了此类试验对合并治疗效应的影响。
对三项已发表的具有代表性的荟萃分析进行有和没有零总事件试验的分析，这些荟萃分析具有不同比例的零总事件试验、治疗效应和异质性，采用逆方差加权法以及纳入研究间异质性的随机效应模型。
在荟萃分析中纳入零总事件试验会使合并治疗效应估计值更接近零，缩小其置信区间并降低研究间异质性。对于RR和OR，纳入此类试验只会引起微小变化，即使它们占纳入试验的绝大多数。对于RD，变化更为显著，在极端情况下可能会消除具有统计学意义的效应估计值。
为了无论选择何种效应量都纳入所有相关数据，综述者在使用OR和RR计算合并估计值时也应纳入零总事件试验。
