title: Vital capacity and COPD: the Swedish CArdioPulmonary bioImage Study (SCAPIS).
abstract: BACKGROUND
  Spirometric diagnosis of chronic obstructive pulmonary disease (COPD) is based on the ratio of forced expiratory volume in 1 second (FEV1)/vital capacity (VC), either as a fixed value <0.7 or below the lower limit of normal (LLN). Forced vital capacity (FVC) is a proxy for VC. The first aim was to compare the use of FVC and VC, assessed as the highest value of FVC or slow vital capacity (SVC), when assessing the FEV1/VC ratio in a general population setting. The second aim was to evaluate the characteristics of subjects with COPD who obtained a higher SVC than FVC.
  
  
  METHODS
  Subjects (n=1,050) aged 50-64 years were investigated with FEV1, FVC, and SVC after bronchodilation. Global Initiative for Chronic Obstructive Lung Disease (GOLD) COPDFVC was defined as FEV1/FVC <0.7, GOLDCOPDVC as FEV1/VC <0.7 using the maximum value of FVC or SVC, LLNCOPDFVC as FEV1/FVC below the LLN, and LLNCOPDVC as FEV1/VC below the LLN using the maximum value of FVC or SVC.
  
  
  RESULTS
  Prevalence of GOLDCOPDFVC was 10.0% (95% confidence interval [CI] 8.2-12.0) and the prevalence of LLNCOPDFVC was 9.5% (95% CI 7.8-11.4). When estimates were based on VC, the prevalence became higher; 16.4% (95% CI 14.3-18.9) and 15.6% (95% CI 13.5-17.9) for GOLDCOPDVC and LLNCOPDVC, respectively. The group of additional subjects classified as having COPD based on VC, had lower FEV1, more wheeze and higher residual volume compared to subjects without any COPD.
  
  
  CONCLUSIONS
  The prevalence of COPD was significantly higher when the ratio FEV1/VC was calculated using the highest value of SVC or FVC compared with using FVC only. Subjects classified as having COPD when using the VC concept were more obstructive and with indications of air trapping. Hence, the use of only FVC when assessing airflow limitation may result in a considerable under diagnosis of subjects with mild COPD.
authors.affiliation: Section of Occupational and Environmental Medicine, Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Kjell
authors.initials: K
authors.lastname: Torén
authors.affiliation: Section of Occupational and Environmental Medicine, Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Anna-Carin
authors.initials: AC
authors.lastname: Olin
authors.affiliation: Department of Public Health and Clinical Medicine, Division of Medicine/Respiratory Medicine, Umeå University, Umeå, Sweden.
authors.forename: Anne
authors.initials: A
authors.lastname: Lindberg
authors.affiliation: Department of Radiology, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Jenny
authors.initials: J
authors.lastname: Vikgren
authors.affiliation: Section of Occupational and Environmental Medicine, Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Linus
authors.initials: L
authors.lastname: Schiöler
authors.affiliation: Department of Radiology, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: John
authors.initials: J
authors.lastname: Brandberg
authors.affiliation: Department of Radiology, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Åse
authors.initials: Å
authors.lastname: Johnsson
authors.affiliation: Department of Clinical Science, Malmö, Lund University, Lund, Sweden.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Engström
authors.affiliation: Department of Respiratory Medicine and Department of Medicine and Health Sciences, Linköping University, Linköping, Sweden.
authors.forename: H Lennart
authors.initials: HL
authors.lastname: Persson
authors.affiliation: Respiratory Medicine Unit, Department of Medicine Solna, Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Sköld
authors.affiliation: Department of Internal Medicine/Lung Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Jan
authors.initials: J
authors.lastname: Hedner
authors.affiliation: Department of Medical Sciences, Clinical Physiology and Respiratory, Allergy and Sleep Research, Uppsala University, Uppsala, Sweden.
authors.forename: Eva
authors.initials: E
authors.lastname: Lindberg
authors.affiliation: Department of Medical Sciences, Clinical Physiology and Respiratory, Allergy and Sleep Research, Uppsala University, Uppsala, Sweden.
authors.forename: Andrei
authors.initials: A
authors.lastname: Malinovschi
authors.affiliation: Department of Translational Medicine, Lund University, Malmö, Sweden.
authors.forename: Eeva
authors.initials: E
authors.lastname: Piitulainen
authors.affiliation: Department of Translational Medicine, Lund University, Malmö, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Wollmer
authors.affiliation: Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Annika
authors.initials: A
authors.lastname: Rosengren
authors.affiliation: Department of Medical Sciences, Clinical Physiology and Respiratory, Allergy and Sleep Research, Uppsala University, Uppsala, Sweden.
authors.forename: Christer
authors.initials: C
authors.lastname: Janson
authors.affiliation: Department of Public Health and Clinical Medicine, Division of Medicine/Respiratory Medicine, Umeå University, Umeå, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Blomberg
authors.affiliation: Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Göran
authors.initials: G
authors.lastname: Bergström
mesh_terms: D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015995:Prevalence; D029424:Pulmonary Disease, Chronic Obstructive / Q000145:classification / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D013147:Spirometry; D013548:Sweden / Q000453:epidemiology; D013997:Time Factors; D014797:Vital Capacity
keywords: air trapping; asthma; epidemiology; general population; obstructive; slow vital capacity; spirometry