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The first article in the series for learners of evidence-based medicine discusses the concept of number needed to treat (NNT).1 However, studies involving patients who need long-term follow-up, such as those with cancer or chronic cardiac conditions, commonly use time-to-event or survival analysis. It is important to realize that the NNT is not calculated in the same way for these studies.
NNT from survival analysis data should be estimated by the hazard ratio2 and is not based on the difference in event rates between treatment groups at the end of follow-up.3
References
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