Define Number Needed to Treat (NNT) according to the material.

Define Number Needed to Treat (NNT) according to the material.

• A. The number of patients with a similar condition I would need to treat to get a positive benefit for one patient
• B. The ratio of the rate of the desired outcome in the experimental group and the rate of the desired outcome in the control or comparison group (the smaller the NNT the better)
• C. The ratio of adverse outcomes between groups
• D. The ratio of sample sizes between groups

Answer: (B)

Number Needed to Treat tells you how many patients must be treated for one additional patient to benefit from the treatment. It is calculated as the reciprocal of the absolute risk reduction (ARR) between the control and treatment groups for the desired outcome. ARR is the difference in event rates: how much the treatment increases the chance of the favorable outcome compared with no treatment. So, NNT = 1 / ARR. For example, if 20% of patients improve with usual care and 40% improve with the new treatment, the ARR is 0.40 − 0.20 = 0.20, and the NNT is 1 / 0.20 = 5. This means you’d need to treat five patients to achieve one additional favorable outcome compared with control. A smaller NNT indicates a more effective intervention. NNT is not a ratio of event rates between groups (that would be relative risk or risk ratio). Instead, it focuses on the absolute difference in outcomes and takes the reciprocal to express how many people need treatment to gain one extra benefit.

Number Needed to Treat tells you how many patients must be treated for one additional patient to benefit from the treatment. It is calculated as the reciprocal of the absolute risk reduction (ARR) between the control and treatment groups for the desired outcome. ARR is the difference in event rates: how much the treatment increases the chance of the favorable outcome compared with no treatment. So, NNT = 1 / ARR.

For example, if 20% of patients improve with usual care and 40% improve with the new treatment, the ARR is 0.40 − 0.20 = 0.20, and the NNT is 1 / 0.20 = 5. This means you’d need to treat five patients to achieve one additional favorable outcome compared with control. A smaller NNT indicates a more effective intervention.

NNT is not a ratio of event rates between groups (that would be relative risk or risk ratio). Instead, it focuses on the absolute difference in outcomes and takes the reciprocal to express how many people need treatment to gain one extra benefit.