Clinical phenotypes of COPD: results of a Japanese epidemiological survey.
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.
Tatsumi
Koichiro
K
Department of Respirology, Graduate School of Medicine, Chiba University, Chiba, Japan. tatsumi@faculty.chiba-u.jp
Kasahara
Yasunori
Y
Kurosu
Katsushi
K
Tanabe
Nobuhiro
N
Takiguchi
Yuichi
Y
Kuriyama
Takayuki
T
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