Prevalence and characteristics of chronic obstructive pulmonary disease in China with a diagnostic criterion of FEV(1)/FVC less than the lower limit of normal—a reanalysis of Chinese epidemiological survey of COPD (CESCOPD) study

BACKGROUND: To reappraise the prevalence and characteristics of chronic obstructive pulmonary disease (COPD) in China with a criterion of FEV(1)/FVC < the lower limit of normal (LLN). METHODS: We assessed the incidence and characteristics of airflow limitation using data from the Chinese Epidemiological Survey of COPD study—a multicenter, randomized trial, with an age-dependent LLN reference equation [established by the Guangzhou Institute of Respiratory Health (GIRH)]. Questionnaire and spirometry data were collected for all eligible subjects. COPD prevalence, risk factors, severity distribution, as well as comparisons of characteristics between the LLN and 0.7 were analyzed. RESULTS: COPD prevalence was 9.0% among participants aged 40–80 years in China with the criterion of LLN. Greater prevalence was observed in female sex, rural areas and never smokers than with the GOLD 0.7 fixed ratio. Age distribution showed a higher incidence of COPD in people under 60 years but lower in participants over 60 years of age. With the LLN FEV(1) reference equation, patients in stage I were decreased (15.8% vs. 24.6%, P<0.001), while the proportion of patients in stage III and IV were increased when compared with the China 2002 revised equation (27.7% vs. 21.1%, for stage III, P<0.001; 8.7% vs. 5.6% for stage IV, P=0.001). Only 30.8% of patients with COPD had ever been “diagnosed” with COPD and 60.6% of the patients had respiratory symptoms, both lower than that under the GOLD 0.7 fixed-ratio criterion (35.5%, P=0.004; 64.8% for symptoms, P=0.014). CONCLUSIONS: With the GIRH-LLN criterion, COPD prevalence was slightly higher, and a large number of women, rural patients and nonsmokers with young age and little symptoms were diagnosed when compared with GOLD 0.7 fixed ratio. These subjects may, therefore, deserve further attention and may warrant regular follow-up. TRIAL REGISTRATION: Registration number: ChiCTR-ECS-13004110.