Using the number needed to treat in clinical practice

The number needed to treat (NNT) is gaining attention as a method of reporting the results of clinical trails with dichotomous outcome measures. The NNT is defined as the number of patients who would need to be treated, on average, with a specific intervention to prevent 1 additional bad outcome or to achieve 1 desirable outcome in a given time period. Because it reports outcomes in terms of patient numbers, it is extremely useful to clinicians for making decisions about the effort expended with a particular intervention to achieve a single positive outcome. This special communication describes the NNT statistic and its utility for choosing clinical interventions.