title: Cluster Analysis in Patients with GOLD 1 Chronic Obstructive Pulmonary Disease.
abstract: BACKGROUND
  We hypothesized that heterogeneity exists within the Global Initiative for Chronic Obstructive Lung Disease (GOLD) 1 spirometric category and that different subgroups could be identified within this GOLD category.
  
  
  METHODS
  Pre-randomization study participants from two clinical trials were symptomatic/asymptomatic GOLD 1 chronic obstructive pulmonary disease (COPD) patients and healthy controls. A hierarchical cluster analysis used pre-randomization demographics, symptom scores, lung function, peak exercise response and daily physical activity levels to derive population subgroups.
  
  
  RESULTS
  Considerable heterogeneity existed for clinical variables among patients with GOLD 1 COPD. All parameters, except forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC), had considerable overlap between GOLD 1 COPD and controls. Three-clusters were identified: cluster I (18 [15%] COPD patients; 105 [85%] controls); cluster II (45 [80%] COPD patients; 11 [20%] controls); and cluster III (22 [92%] COPD patients; 2 [8%] controls). Apart from reduced diffusion capacity and lower baseline dyspnea index versus controls, cluster I COPD patients had otherwise preserved lung volumes, exercise capacity and physical activity levels. Cluster II COPD patients had a higher smoking history and greater hyperinflation versus cluster I COPD patients. Cluster III COPD patients had reduced physical activity versus controls and clusters I and II COPD patients, and lower FEV1/FVC versus clusters I and II COPD patients.
  
  
  CONCLUSIONS
  The results emphasize heterogeneity within GOLD 1 COPD, supporting an individualized therapeutic approach to patients.
  
  
  BACKGROUND
  www.clinicaltrials.gov. NCT01360788 and NCT01072396.
authors.affiliation: Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Québec, Canada.
authors.forename: Philippe
authors.initials: P
authors.lastname: Gagnon
authors.affiliation: Rehabilitation Clinical Trials Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, United States of America.
authors.forename: Richard
authors.initials: R
authors.lastname: Casaburi
authors.affiliation: Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Québec, Canada.
authors.forename: Didier
authors.initials: D
authors.lastname: Saey
authors.affiliation: Rehabilitation Clinical Trials Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, United States of America.
authors.forename: Janos
authors.initials: J
authors.lastname: Porszasz
authors.affiliation: Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Québec, Canada.
authors.forename: Steeve
authors.initials: S
authors.lastname: Provencher
authors.affiliation: Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Québec, Canada.
authors.forename: Julie
authors.initials: J
authors.lastname: Milot
authors.affiliation: Respiratory Epidemiology and Clinical Research Unit, Montréal Chest Institute, McGill University, Montréal, Québec, Canada.
authors.forename: Jean
authors.initials: J
authors.lastname: Bourbeau
authors.affiliation: Queen's University and Kingston General Hospital, Kingston, Ontario, Canada.
authors.forename: Denis E
authors.initials: DE
authors.lastname: O'Donnell
authors.affiliation: Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Québec, Canada.
authors.forename: François
authors.initials: F
authors.lastname: Maltais
mesh_terms: D016022:Case-Control Studies; D016000:Cluster Analysis; D015444:Exercise; D006801:Humans; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012129:Respiratory Function Tests