Prediction of COPD and Related Events Improves by Combining Spirometry and the Single Breath Nitrogen Test

AbstractChronic obstructive pulmonary disease (COPD) develops in small airways. Severity of small airway pathology relates to progression and mortality. The present study evaluated the prediction of COPD of a validated test for small airway disease, i.e. a slope of the alveolar plateau of the single breath nitrogen test (N2-slope). The N2-slope, spirometry, age, smoking habits, and anthropometric variables at baseline were obtained in a population-based sample (n = 592). The cohort was followed for first COPD events (first hospital admission of COPD or related conditions or death from COPD) during 38 years. During follow-up, 52 subjects (8.8%) had a first COPD event, of which 18 (3.0%) died with a first COPD diagnosis. In the proportional hazard regression analysis adjusted for age and smoking habits, the cumulative COPD event incidence increased from 5% among those with high forced expired volume in one second (FEV1) to 25% among those with low FEV1, while increasing from 4% among those with the lowest N...