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Meta-analysis of small randomized controlled trials in surgery may be unreliable
1Vascular Surgery Division, Department of Surgery, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
Background:
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.
Methods:
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.
Results:
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.
Conclusion:
Surgical RCTs tend to be small and underpowered. Meta-analysis of such trials does not necessarily produce reliable results.
