Small airway disease is common in mild COPD and symptomatic subjects at risk with normal spirometry – baseline data from CAPTO-COPD

Background Current guideline-based diagnosis of airflow limitation in COPD focuses on spirometry, which is insensitive to early small airway changes of symptomatic smokers or subjects at risk. We therefore sought to determine the frequency of small airway disease (SAD) in these groups compared with mild COPD and evaluate associations with symptoms as well as health-related quality-of-life (HRQL). Methods Mild COPD patients (post-bronchodilator FEV 1 /VC<70%, FEV 1 ≥70%pred) or (ex)-smokers at risk (post-bronchodilator FEV 1 /VC≥70%, ≥10 pack years, CAT-score ≥10 or long-acting-bronchodilator-treatment) were included in CAPTO-COPD longitudinal observational study. Comprehensive lung function testing included conventional (spirometry, body-plethysmography, TLCO, FeNO) and advanced techniques (oscillometry, multiple-breath- washout). Results We present cross-sectional baseline data from 90 COPD patients (age 65±9 years; mean FEV 1 , 77±12%pred), 62 subjects at risk (60±10, 89±13%pred) and 59 controls (45±19, 98±12%pred). Abnormal SAD-values were found in up to 58% of (ex)-smokers at risk and 60% of COPD patients. Meaningful HRQL differences were most pronounced for SAD-parameters of peripheral resistance (FDR, p=0.03) and elastic lung properties (AX p=0.06, Fres p=0.01). Conclusion SAD is common even in symptomatic (ex)-smokers not fulfilling spirometric criteria with a similar frequency and pattern as compared to mild COPD patients. SAD is associated with impaired HRQL even in patients without established COPD.