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. Therefore, we sought to determine the frequency of small airways disease (SAD) in these groups compared with mild COPD, and evaluate associations with symptoms as well as health-related quality of life (HRQoL). METHODS: Patients with mild COPD (post-bronchodilator forced expiratory volume in 1 s (FEV(1))/forced vital capacity (FVC) <70%, FEV(1) >/=70% predicted) or (ex-)smokers at risk (post-bronchodilator FEV(1)/FVC >/=70%, >/=10 pack-years, COPD Assessment Test score >/=10 or long-acting bronchodilator treatment) were included in the Change in Airway Peripheral Tone in COPD (CAPTO-COPD) longitudinal observational study. Comprehensive lung function testing included conventional (spirometry, body plethysmography, diffusing capacity of the lung for carbon monoxide, exhaled nitric oxide fraction) and advanced techniques (oscillometry, multiple-breath washout). RESULTS: We present cross-sectional baseline data from 90 COPD patients (mean+/-sd age 65+/-9 years; mean+/-sd FEV(1) 77+/-12% pred), 62 subjects at risk (60+/-10 years, 89+/-13% pred) and 59 controls (45+/-199 years, 98+/-12% pred). Abnormal SAD-values were found in up to 58% of (ex-)smokers at risk and 60% of COPD patients. Meaningful HRQoL differences were most pronounced for SAD-parameters of peripheral resistance (frequency dependence of resistance p=0.03) and elastic lung properties (reactance area p=0.06, resonance frequency 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 HRQoL, even in patients without established COPD.
