Significance of FEV3/FEV6 in recognition of early airway disease in smokers at risk of development of COPD: Analysis of the SPIROMICS cohort.

Abstract Background Small airways are known to be affected early in the course of chronic obstructive pulmonary disease (COPD); however, traditional spirometric indices may not accurately identify small airways disease. Research Question Can FEV3/FEV6 identify early airflow abnormalities and predict future clinically important respiratory-related outcomes, including development of COPD? Study Design and Methods We included eight hundred thirty-two current and former smokers with post-bronchodilator FEV1/FVC ≥0.7 from the SPIROMICS cohort. Participants were classified as having a reduced pre-bronchodilator FEV3/FEV6 based on lower limit of normal (LLN) values. Repeatability analysis was performed for FEV3 and FEV6. Regression modeling was used to evaluate the relationship between baseline FEV3/FEV6 and outcome measures including functional small airways disease on thoracic imaging and respiratory exacerbations. Interval censored analysis was used to assess progression to COPD. Results FEV3/FEV6 Interpretation FEV3/FEV6 is a routinely available and repeatable spirometric index which can be useful in the evaluation of early airflow obstruction in current and former smokers without COPD. A reduced FEV3/FEV6 can identify those at risk for future development of COPD and respiratory exacerbations.