Vascular Surgery Division, Department of Surgery, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
Br J Surg. 2010 Apr;97(4):466-9. doi: 10.1002/bjs.6988.
Meta-analysis of randomized controlled trials (RCTs) should provide reliable evidence about the effects of interventions. This may be less reliable when only small trials are available.
The sample size was determined for all surgical RCTs included in Cochrane Collaboration systematic reviews. The difficulty in interpreting meta-analysis of small trials is illustrated using two specific reviews.
The typical sample size for surgical RCTs was small with a median of only 87 participants. Only 39.8 per cent had adequate prerandomization treatment allocation concealment. In both systematic reviews that were assessed in detail, statistically significant early results from meta-analysis of several small RCTs did not reliably predict the results of subsequent RCTs.
Surgical RCTs tend to be small and underpowered. Meta-analysis of such trials does not necessarily produce reliable results.
随机对照试验（RCT）的荟萃分析应该提供干预效果的可靠证据。当只有小型试验可用时，这可能就不太可靠了。
为 Cochrane 协作组系统评价中纳入的所有外科 RCT 确定了样本量。使用两个具体的综述来说明解释小型试验荟萃分析的困难。
外科 RCT 的典型样本量较小，中位数仅为 87 名参与者。仅有 39.8%的试验有充分的随机分组前隐匿。在详细评估的这两个系统综述中，荟萃分析几个小型 RCT 的早期显著结果并不能可靠地预测后续 RCT 的结果。
外科 RCT 往往规模较小且缺乏效力。对这类试验的荟萃分析不一定能产生可靠的结果。
