title: Fixed Cut-Off for FEV1/FEV6 and FEV6 in Detection of Obstructive and Restrictive Patterns.
abstract: BACKGROUND
  Chronic obstructive pulmonary diseases (COPD) have been defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) as irreversible conditions which are diagnosed by fixed cut-off points of FEV1/FVC.
  
  
  OBJECTIVE
  The aim of this study was to determine the cut-off points for FEV1/FEV6 ratio and FEV6 as alternatives for FEV1/FVC and FVC in detection of airway obstruction and lung restriction, respectively.
  
  
  METHODS
  A total of 318 Spiro metric examinations of subjects referred to Shariati hospital were analyzed. A subject was considered to have obstruction if FEV1/FVC was lower than 70%. The restriction was defined as FVC < 80% in the absence of obstruction. The Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of FEV1/FEV6 and FEV6 were calculated.
  
  
  RESULTS
  This study shows that the current cut-off points used to detect obstruction and restriction can be replaced by FEV1/FEV6 < 71% and FEV6 < 83%, respectively. FEV1/FEV6 had sensitivity of 95.5% and specificity of 99.4%; the PPV and NPVs were 99.3% and 96.3%. The prevalence of obstruction was 49.4%. For restrictive pattern, FEV6 had sensitivity of 93%, specificity of 79.5% with PPV of 18% and NPV of 99.5%. The prevalence of restriction was 6.3%.
  
  
  CONCLUSIONS
  The FEV1/FEV6 ratio can be used as a valid surrogate for FEV1/FVC in the diagnosis of airway obstruction, especially for screening purposes in high-risk populations for COPD. Moreover, FEV6 is an acceptable alternative for FVC in detection of restrictive pattern.
authors.affiliation: Endocrine Research Center (Firouzgar), Institute of Endocrinology and Metabolism (Hemmat Campus), Tehran University of Medical Sciences, Tehran, IR Iran.
authors.forename: Rokhsareh
authors.initials: R
authors.lastname: Aghili
authors.forename: Maryam
authors.initials: M
authors.lastname: Kia
authors.forename: Alipasha
authors.initials: A
authors.lastname: Meysamie
authors.forename: Seyed Mojtaba
authors.initials: SM
authors.lastname: Aghili
authors.forename: Omalbanin
authors.initials: O
authors.lastname: Paknejad
keywords: Pulmonary Disease, Chronic Obstructive; Pulmonary Function Tests