Lonnie Wen, PhD
Clinical Education Consultant
Pfizer, Inc.
Objective:
To describe number-needed-to-treat (NNT), its utility, weaknesses, and selected alternatives
Methods:
Didactic presentation of how to calculate, interpret and use NNT to quantify expected therapeutic yield of an intervention; how well absolute measures, like NNT, perform compared to relative measures of therapeutic impact; and how to determine when NNT is most useful in weighing the benefits and harm among competing therapeutic alternatives.
Results:
- NNT is a simple way to express the absolute therapeutic yield of an intervention.
- It is essential to take baseline risk into account when calculating and interpreting absolute or relative measures of therapeutic yield.
- Physicians and patients are more likely to launch interventions based on relative measures of therapeutic yield.
- Patients may have difficulty in understanding what NNT tells them about the benefit/harm associated with an intervention.
Conclusions:
- Use of absolute measures, such as NNT, to describe therapeutic options, lead to more conservative decision-making and are potentially more useful.
- NNTs compared to absolute percent reduction are less frequently understood.
- PDA and web-based tools can assist with calculations.
- These measures are most helpful when best options are not clear or when patient input is needed.
Academic Center for Evidence-Based Nursing