We agree with Zheng and colleagues that a statistical measure of heterogeneity is an important consideration in selecting a fixed or random effects model. However, it should not be considered the sole criterion. In meta‐analyses that include small numbers of trials, such as ours, results of tests for heterogeneity should be interpreted with caution, as they may be underpowered. A fixed effects model has been advocated when meta‐analysing small number of studies (less than five trials), given the concern about inaccurate estimation of between‐study variance (1), as the estimation of τ²(between‐study variance), and therefore of μ (estimate of underlying mean effect), is highly imprecise (2).

中文翻译：

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来信答复：与华法林相比，口服非维生素K口服抗凝剂可能不会显着降低致命或致残性中风的风险。

我们同意郑和同事的观点，异质性的统计量度是选择固定或随机效应模型的重要考虑因素。但是，不应将其视为唯一标准。在像我们这样的仅包含少量试验的荟萃分析中，对于异质性试验的结果应谨慎解释，因为它们可能功能不足。固定效应模型一直主张当元分析给出关于研究间方差的不准确的估计（1）的关注少数研究（小于5次试验），作为τ的估计²（研究间方差），因此，μ（基本均值的估计）非常不精确（2）。