Meta-analysis, Simpson's paradox, and the number needed to treat
نویسندگان
چکیده
BACKGROUND There is debate concerning methods for calculating numbers needed to treat (NNT) from results of systematic reviews. METHODS We investigate the susceptibility to bias for alternative methods for calculating NNTs through illustrative examples and mathematical theory. RESULTS Two competing methods have been recommended: one method involves calculating the NNT from meta-analytical estimates, the other by treating the data as if it all arose from a single trial. The 'treat-as-one-trial' method was found to be susceptible to bias when there were imbalances between groups within one or more trials in the meta-analysis (Simpson's paradox). Calculation of NNTs from meta-analytical estimates is not prone to the same bias. The method of calculating the NNT from a meta-analysis depends on the treatment effect used. When relative measures of treatment effect are used the estimates of NNTs can be tailored to the level of baseline risk. CONCLUSIONS The treat-as-one-trial method of calculating numbers needed to treat should not be used as it is prone to bias. Analysts should always report the method they use to compute estimates to enable readers to judge whether it is appropriate.
منابع مشابه
Simpson's paradox and calculation of number needed to treat from meta-analysis
BACKGROUND Calculation of numbers needed to treat (NNT) is more complex from meta-analysis than from single trials. Treating the data as if it all came from one trial may lead to misleading results when the trial arms are imbalanced. DISCUSSION An example is shown from a published Cochrane review in which the benefit of nursing intervention for smoking cessation is shown by formal meta-analys...
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Title: Simpson's paradox visualized: The example of the Rosiglitazone meta-analysis
متن کاملResponse to reviewer ’ s
Title: Simpson's paradox visualized: The example of the Rosiglitazone meta-analysis
متن کاملSimpson's paradox visualized: The example of the Rosiglitazone meta-analysis
BACKGROUND Simpson's paradox is sometimes referred to in the areas of epidemiology and clinical research. It can also be found in meta-analysis of randomized clinical trials. However, though readers are able to recalculate examples from hypothetical as well as real data, they may have problems to easily figure where it emerges from. METHOD First, two kinds of plots are proposed to illustrate ...
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ورودعنوان ژورنال:
- BMC Medical Research Methodology
دوره 2 شماره
صفحات -
تاریخ انتشار 2002