A hospitalist is reviewing an article from a leading medical journal detailing a phase 3, randomized, double-blind trial. The study evaluated the efficacy and safety of a novel factor XIa inhibitor compared to a placebo for preventing recurrent venous thromboembolism (VTE) in patients with high-risk thrombophilia. A total of 5,200 patients were randomized in a 1:1 ratio to receive either the novel medication or a placebo. The trial summary table is presented below.
| Endpoint | Placebo (n=2,600) | Novel Inhibitor (n=2,600) | p-value |
|---|---|---|---|
| Primary Efficacy (Recurrent VTE or VTE-related death) | 286 (11.0%) | 156 (6.0%) | <0.001 |
| Primary Safety (Major bleeding) | 39 (1.5%) | 65 (2.5%) | 0.012 |
Based on the study results, what is the number needed to treat (NNT) to prevent one primary efficacy endpoint event? (Provide the exact whole number.)
Answer: 20 patients
Answer
20
The Number Needed to Treat (NNT) is calculated as the inverse of the Absolute Risk Reduction (ARR). The primary efficacy endpoint occurred in 11.0% of the placebo group (CER = ) and 6.0% of the novel inhibitor group (EER = ). The ARR is . Therefore, the NNT is . This means 20 patients must be treated with the novel factor XIa inhibitor to prevent one recurrent VTE or VTE-related death.
Step-by-Step Solution
Key Concept
Number Needed to Treat (NNT) Calculation