title: A Novel Spirometric Measure Identifies Mild COPD Unidentified by Standard Criteria.
abstract: BACKGROUND
  In chronic obstructive pulmonary disease, both smaller and larger airways are affected. FEV1mainly reflects large airways obstruction, while the later fraction of forced exhalation reflects reduction in terminal expiratory flow. In this study, the objective was to evaluate the relationship between spirometric ratios, including the ratio of forced expiratory volume in 3 and 6 seconds (FEV3/FEV6), and small airways measures and gas trapping at quantitative chest CT scanning, and clinical outcomes in the Genetic Epidemiology of COPD (COPDGene) cohort.
  
  
  METHODS
  Seven thousand eight hundred fifty-three current and ex-smokers were evaluated for airflow obstruction by using recently defined linear iteratively derived equations of Hansen et al to determine lower limit of normal (LLN) equations for prebronchodilator FEV1/FVC, FEV1/FEV6, FEV3/FEV6, and FEV3/FVC. General linear and ordinal regression models were applied to the relationship between prebronchodilator spirometric and radiologic and clinical data.
  
  
  RESULTS
  Of the 10,311 participants included in the COPDGene phase I study, participants with incomplete quantitative CT scanning or relevant spirometric data were excluded, resulting in 7,853 participants in the present study. Of 4,386 participants with FEV1/FVC greater than or equal to the LLN, 15.4% had abnormal FEV3/FEV6. Compared with normal FEV3/FEV6and FEV1/FVC, abnormal FEV3/FEV6was associated with significantly greater gas trapping; St. George's Respiratory Questionnaire score; modified Medical Research Council dyspnea score; and BMI, airflow obstruction, dyspnea, and exercise index and with shorter 6-min walking distance (all P < .0001) but not with CT scanning evidence of emphysema.
  
  
  CONCLUSIONS
  Current and ex-smokers with prebronchodilator FEV3/FEV6less than the LLN as the sole abnormality identifies a distinct population with evidence of small airways disease in quantitative CT scanning, impaired indexes of physical function and quality of life otherwise deemed normal by using the current spirometric definition.
authors.affiliation: Rehabilitation Clinical Trials Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA; Department of Pulmonary Medicine, Faculty of Medicine, Uludağ University, Bursa, Turkey.
authors.forename: Asli Gorek
authors.initials: AG
authors.lastname: Dilektasli
authors.affiliation: Rehabilitation Clinical Trials Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA.
authors.forename: Janos
authors.initials: J
authors.lastname: Porszasz
authors.affiliation: Rehabilitation Clinical Trials Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA. Electronic address: casaburi@ucla.edu.
authors.forename: Richard
authors.initials: R
authors.lastname: Casaburi
authors.affiliation: Rehabilitation Clinical Trials Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA.
authors.forename: William W
authors.initials: WW
authors.lastname: Stringer
authors.affiliation: Division of Pulmonary, Allergy and Critical Care Medicine, UAB Lung Health Center, University of Alabama at Birmingham, Birmingham, AL.
authors.forename: Surya P
authors.initials: SP
authors.lastname: Bhatt
authors.affiliation: UCLA Clinical and Translational Science Institute, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA.
authors.forename: Youngju
authors.initials: Y
authors.lastname: Pak
authors.affiliation: Rehabilitation Clinical Trials Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA; Faculty of Biological Sciences, University of Leeds, Leeds, England.
authors.forename: Harry B
authors.initials: HB
authors.lastname: Rossiter
authors.affiliation: Brigham and Women's Hospital Clinics, Brigham and Women's Hospital, Boston, MA.
authors.forename: George
authors.initials: G
authors.lastname: Washko
authors.affiliation: Channing Division of Network Medicine and Division of General Internal Medicine and Primary Care, Brigham and Women's Hospital, Boston, MA.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Castaldi
authors.affiliation: Brigham and Women's Hospital Clinics, Brigham and Women's Hospital, Boston, MA.
authors.forename: Raul San Jose
authors.initials: RSJ
authors.lastname: Estepar
authors.affiliation: Rehabilitation Clinical Trials Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA.
authors.forename: James E
authors.initials: JE
authors.lastname: Hansen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000145:classification / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011788:Quality of Life; D018570:Risk Assessment; D012307:Risk Factors; D013147:Spirometry; D014057:Tomography, X-Ray Computed
keywords: COPD; airway obstruction; spirometry; thoracic radiology