Cut-off value of FEV1/FEV6 as a surrogate for FEV1/FVC for detecting airway obstruction in a Korean population

Abstract

Background: Forced expiratory volume in 1 second (FEV₁)/forced expiratory volume in 6 seconds (FEV₆) has been proposed as an alternative to FEV₁/forced vital capacity (FVC) for detecting airway obstruction. A fixed cut-off value for FEV₁/FEV₆ in a Korean population is lacking. We investigated a fixed cut-off for FEV₁/FEV₆ as a surrogate for FEV₁/FVC for detecting airway obstruction. Materials and methods: We used data obtained in the 5 years of the Fifth and Sixth Korean National Health and Nutrition Examination Survey. A total of 14,978 participants aged ≥40 years who underwent spirometry adequately were the study cohort. “Airway obstruction” was a fixed cut-off FEV₁/FVC 1/FVC lower limit of normal. Results: Among the 14,978 participants (43.5% male, 56.5% female; mean age: 56.9 years for men and 57.0 years for women), 14.0% had obstructive lung function according to a fixed cut-off FEV₁/FVC 1/FEV₆ cut-off for predicting FEV₁/FVC 1/FEV₆ showed 93.8% sensitivity, 94.8% specificity, 74.7% positive predictive value, 98.9% negative predictive value, and 0.8 Cohen’s kappa coefficient. When compared with FEV₁/FVC < lower limit of normal, FEV₁/FEV₆ 1/FVC 1 (%), FEV₁/FEV₆ 1/FVC Conclusion: A valid fixed cut-off for detecting airway obstruction in a Korean population is FEV₁/FEV₆ of 75%, but should be used with caution in older individuals and those with mild–moderate airway obstruction.