A recent multi-center, randomized, double-blind clinical trial evaluated the efficacy of a novel monoclonal antibody for the prevention of episodic migraines. The published abstract includes the following data regarding the primary endpoint:
| Outcome at 12 Months | Placebo (n = 400) | Treatment Group (n = 400) |
|---|---|---|
| Progression to chronic migraine | 15% | 5% |
Based on these reported event rates, what is the number needed to treat (NNT) to prevent one additional patient from progressing to chronic migraine?
Answer: 10 patients
Answer
10
The Number Needed to Treat (NNT) is mathematically defined as the inverse of the Absolute Risk Reduction (ARR). In this clinical trial, the control event rate (progression to chronic migraine in the placebo group) is () and the experimental event rate (progression in the treatment group) is (). The ARR is calculated by subtracting the experimental event rate from the control event rate: . Finally, the NNT is calculated by taking the inverse of the ARR: . This indicates that patients need to receive the novel monoclonal antibody over a -year period to prevent one additional progression to chronic migraine.
Step-by-Step Solution
Key Concept
Number Needed to Treat (NNT) Calculation