American Board of Internal Medicine (ABIM) Certification Practice Exam

What does the Number Needed to Treat (NNT) signify?

1. The number of patients required for surgery

2. The number of patients treated to prevent one bad outcome

3. The total number of treatments performed in the study

4. The average duration of treatment

The correct answer is: The number of patients treated to prevent one bad outcome

The Number Needed to Treat (NNT) is a crucial concept in clinical medicine that reflects the effectiveness of a treatment intervention. Specifically, it signifies the number of patients who must be treated in order to prevent one adverse outcome, such as a heart attack, stroke, or death. A lower NNT indicates a more effective treatment, as it means fewer patients need to be treated to achieve a beneficial outcome. In practice, calculating the NNT involves comparing the incidence of an adverse outcome in the control group versus the treatment group. The formula for NNT is derived from the absolute risk reduction (ARR), which represents the difference in event rates between the two groups. Thus, the NNT can help clinicians and patients evaluate the benefits of a treatment against its risks and costs. The other options do not accurately describe the NNT: the number of patients required for surgery pertains to surgical indications, the total number of treatments performed in a study relates to the scale of the trial rather than its outcomes, and the average duration of treatment does not reflect the effectiveness or necessity of treating patients to achieve specific health benefits.