Reduced FEV3/FVC as an Early Indicator of COPD in Individuals with Normal Spirometry: A Prospective Analysis from the ECOPD Study.

PURPOSE: This study aimed to evaluate the association between the forced expiratory volume in 3 s (FEV3) to forced vital capacity (FVC) and computed tomography (CT)-defined abnormalities, and to assess its potential value in predicting incident chronic obstructive pulmonary disease (COPD) over a 3-year period.

PARTICIPANTS AND

METHODS

This 3-year community-based cohort study enrolled participants with normal lung function (post-bronchodilator FEV1/FVC ≥ 0.70 and FEV1 ≥ 80% predicted). Baseline assessments included questionnaires, spirometry, CT scans, and impulse oscillometry. Participants were stratified by post-bronchodilator FEV3/FVC tertiles. Outcomes included acute respiratory events, annual lung function decline, and COPD incidence. Data were analyzed using mixed-effects models, log-binomial regression, and zero-inflated negative binomial models.

RESULTS

Of the 981 participants with normal baseline lung function stratified by post-bronchodilator FEV3/FVC tertiles (high: ≥95.5%, medium: 91.9-95.4%, low: ≤91.8%), 807 completed the 3-year follow-up. Compared to the high-FEV3/FVC group, participants in the low-FEV3/FVC group tended to be older (60.5 vs 55.7 years) and included more males (80.4% vs 38.8%) and smokers. The low-FEV3/FVC group also demonstrated a lower baseline post-bronchodilator FEV1/FVC (74.0% vs 85.1%) and higher prevalence of emphysema (53.5% vs 18.3%). Longitudinal analysis revealed a greater annual post-bronchodilator FEV1 decline in the low-FEV3/FVC group (adjusted mean difference: 10 mL, 95% confidence interval [CI]: 0 to 21mL; p = 0.043) and an increased risk of developing COPD (19.4% versus 1.9%; adjusted relative risk: 4.96, 95% CI: 1.96-12.51; p = 0.001) than the high-FEV3/FVC group, with no difference in acute respiratory events.

CONCLUSION

A reduced FEV3/FVC ratio was associated with an increased risk of accelerated lung function decline and progression to COPD in individuals with normal spirometry. As a readily accessible measure derived from routine spirometry, FEV3/FVC may have a role in early COPD detection.