Soru

A 68-year-old man with severe chronic obstructive pulmonary disease (COPD) presents for a follow-up visit. He has had multiple hospitalizations over the past year despite maximal inhaled therapy. His physician is considering prescribing a newly approved targeted biologic therapy.

To evaluate its efficacy, the physician reviews a recent phase III randomized controlled trial. In this trial, 4,000 patients with severe COPD were randomized equally to receive either the biologic therapy or a placebo, in addition to standard care. Over a 2-year follow-up period, 300 patients in the placebo group and 200 patients in the biologic group experienced a severe exacerbation requiring hospitalization. The study reported that this risk difference was statistically significant ($p < 0.01$) with a 95% confidence interval for the relative risk of 0.55 to 0.81.

Using a validated clinical prediction tool, the physician calculates that this specific patient has a baseline 2-year risk of 30% for experiencing a severe exacerbation on his current regimen. Assuming the relative risk reduction observed in the trial is constant across different baseline risk strata, what is the estimated number needed to treat (NNT) to prevent one severe exacerbation over 2 years for patients with a baseline risk profile identical to this man?