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Int J Epidemiol. 2009 Feb;38(1):276-86. doi: 10.1093/ije/dyn179. Epub 2008 Sep 29.

Can trial sequential monitoring boundaries reduce spurious inferences from meta-analyses?

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  • 1Copenhagen Trial Unit, Center for Clinical Intervention Research, Copenhagen University Hospital, Department 3344, Blegdamsvej 9, DK-2100 Copenhagen, Denmark.



Results from apparently conclusive meta-analyses may be false. A limited number of events from a few small trials and the associated random error may be under-recognized sources of spurious findings. The information size (IS, i.e. number of participants) required for a reliable and conclusive meta-analysis should be no less rigorous than the sample size of a single, optimally powered randomized clinical trial. If a meta-analysis is conducted before a sufficient IS is reached, it should be evaluated in a manner that accounts for the increased risk that the result might represent a chance finding (i.e. applying trial sequential monitoring boundaries).


We analysed 33 meta-analyses with a sufficient IS to detect a treatment effect of 15% relative risk reduction (RRR). We successively monitored the results of the meta-analyses by generating interim cumulative meta-analyses after each included trial and evaluated their results using a conventional statistical criterion (alpha = 0.05) and two-sided Lan-DeMets monitoring boundaries. We examined the proportion of false positive results and important inaccuracies in estimates of treatment effects that resulted from the two approaches.


Using the random-effects model and final data, 12 of the meta-analyses yielded P > alpha = 0.05, and 21 yielded P </= alpha = 0.05. False positive interim results were observed in 3 out of 12 meta-analyses with P > alpha = 0.05. The monitoring boundaries eliminated all false positives. Important inaccuracies in estimates were observed in 6 out of 21 meta-analyses using the conventional P </= alpha = 0.05 and 0 out of 21 using the monitoring boundaries.


Evaluating statistical inference with trial sequential monitoring boundaries when meta-analyses fall short of a required IS may reduce the risk of false positive results and important inaccurate effect estimates.

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