Abstract
Clinicians are presented with research study reports suggesting advantages of one medication over another. There is an urgent need for clinicians to learn the intuitive and simple tools of Evidence-Based Medicine (EBM) that can be used on a day-to-day basis to evaluate clinical research evidence.
One such technique is Number Needed to Treat (NNT). NNT is easy to calculate for categorical outcomes: it is the reciprocal of the percentage difference between the two outcomes.
Clinical trial results expressed as NNT can be easily summarized and communicated effectively to patients and their families. Limitations include ensuring that the NNT is calculated from research that enrolls subjects similar to patients that one treats in actual clinical practice, with doses of medications similar to what is used in the real world.
Direct calculation of NNT is limited to binary or dichotomous outcomes. However, NNT can be used to assess both advantages and disadvantages between two competing interventions.
A single digit NNT (less than 10) will mean that you will encounter this difference between interventions in routine clinical practice. Before accepting that a statistically significant clinical trial result is important to you and your patients, calculate the NNT.
NNT will tell you if the clinical trial result is compelling or if it is irrelevant