ORIGINAL ARTICLE

Chronic obstructive pulmonary disease in the absence of chronic bronchitis in China resp_1817

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MING LU1, WANZHEN YAO1, NANSHAN ZHONG2, YUMIN ZHOU2, CHEN WANG3, PING CHEN4, JIAN KANG5, SHAOGUANG HUANG6, BAOYUAN CHEN7, CHANGZHENG WANG8, DIANTAO NI9, XIAOPING WANG10, DALI WANG11, SHENGMING LIU2,12, JIACHUN LU13, NING SHEN1 AND PIXIN RAN2 1

Department of Respiratory Medicine of Peking University Third Hospital and 3Beijing Institute of Respiratory Medicine, Beijing Chaoyang Hospital, Capital University of Medical Science, Beijing, 2The State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Diseases, The First Affiliated Hospital, Guangzhou Medical University, 11Department of Respiratory Medicine of Second Hospital of Liwan District of Guangzhou, 12Department of Respiratory Medicine of First Affiliated Hospital of Jinan University and 13 Department of Epidemiology, Guangzhou Medical University, Guangzhou, 4Department of Respiratory Medicine of Shenyang Military General Hospital and 5Department of Respiratory Medicine of First Affiliated Hospital of China Medical University, Shenyang, 6Department of Respiratory Medicine of Ruijin Hospital of Shanghai Jiao Tong University School of Medicine, Shanghai, 7Department of Respiratory Medicine of Tianjin Medical University General Hospital, Tianjin, 8Department of Respiratory Medicine of Xinqiao Hospital of Third Military Medical University, Chongqing, 9Department of Respiratory Medicine of Xijing Hospital of Fourth Military Medical University, Xi’an, and 10Department of Respiratory Medicine of First Municipal People Hospital of Shaoguan, Shaoguan, China

ABSTRACT

SUMMARY AT A GLANCE

Background and objective: COPD has a variable natural history and not all individuals follow the same course. The aim of this study was to assess the prevalence of COPD in the absence of chronic bronchitis (CB) based on a population survey in China, and to identify the determinants of CB in patients with COPD. Methods: A multi-stage cluster sampling strategy was used to survey a population from seven different provinces/cities of China. All residents over 40 years of age were interviewed using a standardized questionnaire and spirometry was measured. A postbronchodilator FEV1/FVC < 70% was defined as the diagnostic criterion for COPD. All COPD patients who were screened were divided into two groups according to the presence or absence of CB. Results: Of the population of 20 245 that was surveyed, 70% of the 1668 patients who were diagnosed with COPD reported no history of CB. The ages, BMI and comorbidities of COPD patients with or without CB were similar. Male gender, residence in a rural area, having a lower level of education, exposure to tobacco

Chronic bronchitis was once thought to be a principal component of COPD; however, it has not been specifically incorporated into the definition of COPD in recent guidelines, suggesting that its perceived importance in the diagnosis of COPD may have diminished. This study assessed the current prevalence of COPD without chronic bronchitis in China.

Correspondence: Pixin Ran, The State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Diseases, The First Affiliated Hospital, Guangzhou Medical University, 195 Dongfeng Xi Road, Guangzhou, Guangdong 510182, China. Email: [email protected] Received 25 March 2010; invited to revise 3 May 2010; revised 14 May 2010; accepted 18 May 2010 (Associate Editor: Chi Chiu Leung). © 2010 The Authors Respirology © 2010 Asian Pacific Society of Respirology

smoke or biomass fuels, poor ventilation in the kitchen and a family history of respiratory disease were all associated with a higher risk of COPD with CB. Patients without CB had less difficulty in walking and higher FEV1/FVC values than patients with CB, but were more likely to be underdiagnosed. The strongest predictors of CB were male gender, current smoking and severity of dyspnoea. Conclusions: This survey confirmed that there is a high prevalence of COPD in the absence of CB in China. It appears that CB is not essential to the diagnosis of COPD. Key words: chronic bronchitis, chronic obstructive pulmonary disease, clinical epidemiology, cough.

INTRODUCTION COPD affects tens of millions of individuals, limits the functional capacity of many and has become a Respirology (2010) 15, 1072–1078 doi: 10.1111/j.1440-1843.2010.01817.x

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COPD without chronic bronchitis

serious public health problem worldwide. Unfortunately, although COPD is preventable, it is vastly underappreciated and underdiagnosed for many reasons, and patients usually underperceive the magnitude of their problem and accept the limitations associated with progression of the disease as being natural for an older person who has smoked.1–4 The term ‘chronic bronchitis’ (CB) was introduced into the medical literature early in the 19th century. In 1986, CB and emphysema were recognized in an American Thoracic Society statement as the two main components of COPD.5 However, the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines published in 20016 provided a definition of COPD that differed from previous statements, and did not incorporate the term ‘CB’ into the definition. From then on, the term ‘CB’ has not appeared in the definition of COPD used in recent guidelines,4,6,7 because it does not reflect the major impact of airflow limitation on morbidity and mortality in COPD patients,4 and not all patients with CB will develop COPD.8,9 This reflects the altered understanding of COPD. While there has been greater emphasis on airflow limitation in COPD, it appeared that CB was not required for the diagnosis of COPD. Indeed, some patients may even present with chronic hypercapnic respiratory failure before being diagnosed as having COPD, and these patients usually do not provide any history of CB. Despite this, it is clear that CB remains a useful term not only in clinical practice but also for epidemiological purposes. The role of CB in COPD has been less well investigated.9,10 and there is little research explicitly demonstrating that CB has limited value for the diagnosis of COPD. The aim of the present study was to assess the prevalence of COPD in patients with or without CB, based on a large, population survey in China. In addition, we also aimed to identify the determinants of CB.

METHODS Study design and subject selection This was an epidemiological survey of COPD in China in 2003.11 The population-based, crosssectional survey was conducted in seven provinces/ cities in China: Beijing, Tianjin and Liaoning (northern China); Shanghai (eastern China); Guangdong (southern China); and Shanxi and Chongqing (western China). The study protocol was approved by the institutional review board at each participating centre.

Questionnaires and spirometry All recruited residents were individually interviewed by trained interviewers using a standardized questionnaire, which was a revision of the International Burden of Obstructive Lung Disease Initiative questionnaire,12 and incorporated parts of questionnaires used for previous COPD studies in China.13 The questionnaire covered demographic data, respi© 2010 The Authors Respirology © 2010 Asian Pacific Society of Respirology

ratory symptoms, nutritional status, risk factors, comorbidities, and past medical and family history. Portable spirometers (Micro Medical Ltd, Chatham, Kent, UK) were used in accordance with the procedure recommended by the American Thoracic Society.14 Subjects with airflow limitation underwent post-bronchodilator testing 15–20 min after inhaling 200 mg of salbutamol through a 500-mL spacer.

Definitions and grouping of subjects Based on the GOLD 2008 criteria,4 subjects with post-bronchodilator FEV1/FVC < 70% we defined as having COPD. CXR were performed on all subjects identified as having COPD, in order to exclude patients with other respiratory diseases that may affect lung function, such as tuberculosis and bronchiectasis. The severity of ventilatory impairment was also classified according to the GOLD criteria as:4 mild, FEV1 ⱖ 80% of predicted; moderate, 50% ⱕ FEV1 < 80%; severe, 30% ⱕ FEV1 < 50%; and very severe, FEV1 < 30%. The Medical Research Council dyspnoea scale, as modified by Bestall et al.,15 was incorporated into the questionnaire, as a measure of the severity of dyspnoea. The classical definition of CB was used: cough and sputum expectoration on most days for at least 3 months of the year and for at least two consecutive years, after exclusion of other pulmonary or cardiac causes of chronic productive cough.16 Patients who met the criteria for CB were categorized as the group with CB. Patients who did not meet the criteria were designated as the group without CB.

Statistical analyses Descriptive data were expressed as mean ⫾ SD and frequencies were expressed as number (%). Differences between the two groups were tested for significance using Student’s t-test or the chi-square test. Potential determinants of CB were entered into the final multivariate logistic regression model using the backward stepwise method. A P-value < 0.05 was deemed to indicate statistical significance. Statistical analyses were performed using SPSS version 11.0.

RESULTS Of the 25 627 subjects sampled from seven provinces/ cities, 20 245 completed questionnaires and produced acceptable spirometry, yielding a response rate of 79%. A total of 1668 subjects were diagnosed with COPD and included in the study. Among these, only 500 (30%) reported a history of CB, while 1168 (70%) had no history of CB.

Demographic characteristics of the sample population Patients were stratified on the basis of demographic and social characteristics, as well as comorbidities Respirology (2010) 15, 1072–1078

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M Lu et al. Demographic and other details of the COPD patients after stratification into groups with or without CB COPD

Variable Total number (%)

Group without CB 1168 (70)

Group with CB

P-value*

500 (30)