Understanding The Number Needed to Treat.

The number needed to treat (NNT) is the inverse of the absolute risk difference, which is used as a secondary outcome to clinical trials as a measure relevant to a positive trial, supplementing statistical significance. The NNT requires dichotomous outcomes and is influenced by the baseline disease or symptom severity, the particular population, the type and intensity of the interventional, the duration of treatment, the time period to assessment of response, and the comparator response. Confidence intervals should always accompany NNT for the precision of its estimate. In this review, three meta-analyses are reviewed, which included the NNT in the analysis of response.