title: Clinical phenotypes of COPD: results of a Japanese epidemiological survey.
abstract: OBJECTIVE
  The Global Initiative for Obstructive Lung Disease characterizes COPD as airflow limitation caused by parenchymal destruction and/or small airway disease. This report characterizes the clinical features of these two phenotypes of COPD in Japan.
  
  
  METHODS
  COPD was diagnosed by spirometric airflow limitation (FEV(1)/FVC < 70%), and all subjects underwent chest CT scanning. Patients with diffuse low attenuation areas (LAA) on CT scan were categorized as the emphysema-dominant phenotype; those with little LAA were categorized as the airway disease-dominant phenotype. The two groups were compared to identify significant clinical or demographic differences.
  
  
  RESULTS
  Of the 1438 patients analysed, 1294 (90%) were classified as having an emphysema-dominant phenotype and 144 (10%) as having an airway disease-dominant phenotype. The airway disease-dominant phenotype was: more common than the emphysema-dominant phenotype in women (15%vs. 7%, P < 0.01) and in non-smokers (6%vs. 2%, P < 0.05); was more commonly complicated by asthmatic features (35%vs. 21%, P < 0.01); and had higher IgE and eosinophil levels (P < 0.05) and less lung function impairment.
  
  
  CONCLUSIONS
  This analysis is the first to clinically define two phenotypes of COPD in a Japanese epidemiological survey. There appear to be striking differences as well as overlap between these two groups. Further research is warranted to determine the significance of COPD phenotypes.
authors.affiliation: Department of Respirology, Graduate School of Medicine, Chiba University, Chiba, Japan. tatsumi@faculty.chiba-u.jp
authors.forename: Koichiro
authors.initials: K
authors.lastname: Tatsumi
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Kasahara
authors.forename: Katsushi
authors.initials: K
authors.lastname: Kurosu
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Tanabe
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Takiguchi
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kuriyama
mesh_terms: D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D010641:Phenotype; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology; D012129:Respiratory Function Tests; D013147:Spirometry