title: 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.
  
  
  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 <70% according to the Global Initiative for Chronic Obstructive Lung Disease guidelines. We also used European Respiratory Society/Global Lung Initiative 2012 equations for the FEV1/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 <70%. Optimal FEV1/FEV6 cut-off for predicting FEV1/FVC <70% was 75% using receiver operating characteristic curve analyses (area under receiver operating characteristic curve =0.989, 95% confidence interval 0.987-0.990). This fixed cut-off of FEV1/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 <75% tended to over-diagnose airflow limitation (just like a fixed cut-off of FEV1/FVC <70%). When grouped according to age and FEV1 (%), FEV1/FEV6 <75% diagnosed more airway obstruction in older participants and mild-moderate stages compared with FEV1/FVC <70%.
  
  
  CONCLUSIONS
  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.
authors: Division of Pulmonology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea; Institute of Chest Disease, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors: Kyung Soo
authors: KS
authors: Chung
authors: Division of Pulmonology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea; Institute of Chest Disease, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors: Ji Ye
authors: JY
authors: Jung
authors: Division of Pulmonology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea; Institute of Chest Disease, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors: Moo Suk
authors: MS
authors: Park
authors: Division of Pulmonology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea; Institute of Chest Disease, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors: Young Sam
authors: YS
authors: Kim
authors: Division of Pulmonology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea; Institute of Chest Disease, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors: Se Kyu
authors: SK
authors: Kim
authors: Division of Pulmonology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea; Institute of Chest Disease, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors: Joon
authors: J
authors: Chang
authors: Division of Pulmonology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea; Institute of Chest Disease, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors: Joo Han
authors: JH
authors: Song
mesh_terms: D000328:Adult; D000368:Aged; D000402:Airway Obstruction / Q000175:diagnosis* / Q000503:physiopathology; D019540:Area Under Curve; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000503:physiopathology; D012372:ROC Curve; D015203:Reproducibility of Results; D056910:Republic of Korea; D013147:Spirometry; D014797:Vital Capacity
keywords: airway obstruction; chronic obstructive pulmonary disease; forced expiratory volume in 6 seconds; pulmonary function test