title: Identification and prospective validation of clinically relevant chronic obstructive pulmonary disease (COPD) subtypes.
abstract: BACKGROUND
  Chronic obstructive pulmonary disease (COPD) is increasingly considered a heterogeneous condition. It was hypothesised that COPD, as currently defined, includes different clinically relevant subtypes.
  
  
  METHODS
  To identify and validate COPD subtypes, 342 subjects hospitalised for the first time because of a COPD exacerbation were recruited. Three months after discharge, when clinically stable, symptoms and quality of life, lung function, exercise capacity, nutritional status, biomarkers of systemic and bronchial inflammation, sputum microbiology, CT of the thorax and echocardiography were assessed. COPD groups were identified by partitioning cluster analysis and validated prospectively against cause-specific hospitalisations and all-cause mortality during a 4 year follow-up.
  
  
  RESULTS
  Three COPD groups were identified: group 1 (n=126, 67 years) was characterised by severe airflow limitation (postbronchodilator forced expiratory volume in 1 s (FEV(1)) 38% predicted) and worse performance in most of the respiratory domains of the disease; group 2 (n=125, 69 years) showed milder airflow limitation (FEV(1) 63% predicted); and group 3 (n=91, 67 years) combined a similarly milder airflow limitation (FEV(1) 58% predicted) with a high proportion of obesity, cardiovascular disorders, diabetes and systemic inflammation. During follow-up, group 1 had more frequent hospitalisations due to COPD (HR 3.28, p<0.001) and higher all-cause mortality (HR 2.36, p=0.018) than the other two groups, whereas group 3 had more admissions due to cardiovascular disease (HR 2.87, p=0.014).
  
  
  CONCLUSIONS
  In patients with COPD recruited at their first hospitalisation, three different COPD subtypes were identified and prospectively validated: 'severe respiratory COPD', 'moderate respiratory COPD', and 'systemic COPD'.
authors.affiliation: Centre for Research in Environmental Epidemiology, Doctor Aiguader 88, 08003 Barcelona, Catalonia, Spain. jgarcia@creal.cat
authors.forename: Judith
authors.initials: J
authors.lastname: Garcia-Aymerich
authors.forename: Federico P
authors.initials: FP
authors.lastname: Gómez
authors.forename: Marta
authors.initials: M
authors.lastname: Benet
authors.forename: Eva
authors.initials: E
authors.lastname: Farrero
authors.forename: Xavier
authors.initials: X
authors.lastname: Basagaña
authors.forename: Àngel
authors.initials: À
authors.lastname: Gayete
authors.forename: Carles
authors.initials: C
authors.lastname: Paré
authors.forename: Xavier
authors.initials: X
authors.lastname: Freixa
authors.forename: Jaume
authors.initials: J
authors.lastname: Ferrer
authors.forename: Antoni
authors.initials: A
authors.lastname: Ferrer
authors.forename: Josep
authors.initials: J
authors.lastname: Roca
authors.forename: Juan B
authors.initials: JB
authors.lastname: Gáldiz
authors.forename: Jaume
authors.initials: J
authors.lastname: Sauleda
authors.forename: Eduard
authors.initials: E
authors.lastname: Monsó
authors.forename: Joaquim
authors.initials: J
authors.lastname: Gea
authors.forename: Joan A
authors.initials: JA
authors.lastname: Barberà
authors.forename: Àlvar
authors.initials: À
authors.lastname: Agustí
authors.forename: Josep M
authors.initials: JM
authors.lastname: Antó
mesh_terms: D000368:Aged; D004812:Epidemiologic Methods; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D008019:Life Style; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D011379:Prognosis; D029424:Pulmonary Disease, Chronic Obstructive / Q000145:classification* / Q000175:diagnosis / Q000401:mortality / Q000503:physiopathology; D012923:Social Class; D013030:Spain / Q000453:epidemiology
chemical_list: D010100:Oxygen