title: Characterisation of phenotypes based on severity of emphysema in chronic obstructive pulmonary disease.
abstract: BACKGROUND
  Airflow limitation in chronic obstructive pulmonary disease (COPD) is caused by a mixture of small airway disease and emphysema, the relative contributions of which may vary among patients. Phenotypes of COPD classified purely based on severity of emphysema are not well defined and may be different from the classic phenotypes of "pink puffers" and "blue bloaters".
  
  
  METHODS
  To characterise clinical phenotypes based on severity of emphysema, 274 subjects with COPD were recruited, excluding those with physician-diagnosed bronchial asthma. For all subjects a detailed interview of disease history and symptoms, quality of life (QOL) measurement, blood sampling, pulmonary function tests before and after inhalation of salbutamol (0.4 mg) and high-resolution CT scanning were performed.
  
  
  RESULTS
  Severity of emphysema visually evaluated varied widely even among subjects with the same stage of disease. No significant differences were noted among three groups of subjects classified by severity of emphysema in age, smoking history, chronic bronchitis symptoms, blood eosinophil count, serum IgE level or bronchodilator response. However, subjects with severe emphysema had significantly lower body mass index (BMI) and poorer QOL scores, evaluated using St George's Respiratory Questionnaire (SGRQ), than those with no/mild emphysema (mean (SD) BMI 21.2 (0.5) vs 23.5 (0.3) kg/m(2), respectively; SGRQ total score 40 (3) vs 28 (2), respectively; p<0.001 for both). These characteristics held true even if subjects with the same degree of airflow limitation were chosen.
  
  
  CONCLUSIONS
  The severity of emphysema varies widely even in patients with the same stage of COPD, and chronic bronchitis symptoms are equally distributed irrespective of emphysema severity. Patients with the phenotype in which emphysema predominates have lower BMI and poorer health-related QOL.
authors.affiliation: First Department of Medicine, Hokkaido University School of Medicine, Sapporo, Japan.
authors.forename: Hironi
authors.initials: H
authors.lastname: Makita
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Nasuhara
authors.forename: Katsura
authors.initials: K
authors.lastname: Nagai
authors.forename: Yoko
authors.initials: Y
authors.lastname: Ito
authors.forename: Masaru
authors.initials: M
authors.lastname: Hasegawa
authors.forename: Tomoko
authors.initials: T
authors.lastname: Betsuyaku
authors.forename: Yuya
authors.initials: Y
authors.lastname: Onodera
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Hizawa
authors.forename: Masaharu
authors.initials: M
authors.lastname: Nishimura
mesh_terms: D006801:Humans; D010641:Phenotype; D029424:Pulmonary Disease, Chronic Obstructive / Q000235:genetics*; D011656:Pulmonary Emphysema / Q000235:genetics*; D012720:Severity of Illness Index