Numbers needed to treat derived from meta-analyses---sometimes informative, usually misleading

Numbers needed to treat derived from meta-analysis: a word of caution.

In the editorial by Drs Marx and Bucher in the March/April 2003 issue of Evidence-Based Medicine, an example illustrating the application of estimates of RRRs to individual risk is misleading. In their example, Marx and Bucher state that the NNTwould increase in patients with a baseline risk 11 times that of the low risk group, which is counterintuitive. If a high risk patient is judged to have...

Numbers needed to treat to prevent tuberculosis.

A new action framework advocacy document for tuberculosis elimination in low-incidence countries has recently been published in this journal [1]. We completely agree with the importance of addressing the goal of elimination of tuberculosis, which may be achievable in regions such as Western Europe and North America, but we are concerned that this goal may be overly ambitious at this point in ti...

Measures of clinical effectiveness: the numbers needed to treat.

Meta-analysis, Simpson's paradox, and the number needed to treat

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 e...

Number Needed to Treat