Abstract
Background: GIRD COPD Biobank is a multicenter observational study blood-based database with local characteristics, in order to investigate the causes, risk factors, pathogenesis, prevalence patterns and trends of COPD and promote new pathogenic insights in China.
Methods: We enrolled 855 clinically COPD patients and 660 controls with normal lung function. Extensive data collection has been undertaken with questionnaires, clinical measurements, and collection and storage of blood specimens, following Standard Operating Procedures (SOP). All surveys had similar quality controls, supervisions, and training of the investigator team.
Results: Since September 2010, a total of 1515 subjects (1116 [73.7%] males; 855 [56.4%] diagnosed with COPD) were enrolled. Analyses of the design and interim results of the GIRD COPD Biobank Study identified patients with COPD were older, lower educational level, a longer history of pack-year smoking, less in kitchen fan usage, X-ray exposure, and history of disease (P < 0.01 for all); Most of the COPD subjects belonged to moderately severe or worse, stratified according to Global Lung Function Initiative (GLI); COPD patients had relatively more co-morbidities than controls; Environmental hazard exposures might be the main contributors to the reported respiratory symptoms; Cold air, haze, and influenza acted the top three factors to induce respiratory symptoms in both COPD cases and controls.
Conclusion: The GIRD COPD Biobank Study has the potential to provide substantial novel insights into the genetics, biomarkers, environmental and lifestyle aspects of COPD. It is expected to provide new insights for pathogenesis and the long-term progression of COPD.
| Abbreviations | ||
| COPD | = | chronic obstructive pulmonary disease |
| FEV 1 | = | forced expiratory volume in 1 second |
| FVC | = | forced vital capacity |
| BMI | = | Body mass index |
| SOP | = | Standard Operating Procedures |
| GLI | = | Global Lung Function Initiative. |
Introduction
Chronic obstructive pulmonary disease (COPD) is defined by the presence of poorly reversible airflow limitation (Citation1). It is a complex, multi-component, heterogeneous disease, whose clinical, functional, and radiological presentation varies greatly from patient to patient despite having a similar degree of airflow limitation (Citation1–3). They may have multiple causes with contributions from genetic factors, environmental exposures, co-morbidities, and age-related degenerative changes. Unfortunately, the prevalence, distribution, and inter-relationships of the main clinical, functional, and radiological manifestations of the disease in a large, well-characterised and controlled population of patients are lacking. Especially, while several biobank studies of COPD are currently ongoing in Western countries (Citation4–6), longitudinal studies have seldom been conducted in China. In terms of ethnic heterogeneity, there is a need to initial longitudinal studies of COPD patients in China. Therefore, COPD blood bank was set up by Guangzhou Institute of Respiratory Disease and State Key Laboratory of Respiratory Disease (GIRD), Guangzhou, PR, China for such purpose, meanwhile to optimize the use of biological specimens.
GIRD COPD Biobank Study is an ongoing multicenter observational project. The aims of the GIRD COPD Biobank were to augment the detection of novel genes and biomarkers, promote new pathogenic insights, and identify interactive prognostic factors for COPD in Chinese population. This study has the potential to provide scientific evidence for strategic planning of COPD prevention and control, and development of new treatment and intervention approaches. The present article mainly describes the design and interim results of the GIRD COPD Biobank project.
Materials and Methods
Subjects
COPD cases and controls were genetically unrelated ethnic Han Chinese and were from Guangzhou City. Patients with COPD were mainly consecutively recruited in Respiratory Medicine Department, The First Affiliated Hospital of Guangzhou Medical University. The controls were randomly selected from the Health Examination Center of the same hospital during the same time period when patients were recruited. The GIRD COPD Biobank collection was initiated in 2010 to store blood specimens of patients and controls as a resource for research purposes. Matching criteria of patients and controls were: age between 40–80, and permanent residents (lived in Guangzhou for years). Each individual was invited to sign informed consent, offer access to medical records, retrieve his/her management information before and after hospitalization, and donate blood material for research usage.
The inclusion criteria for the GIRD Biobank Study were patients over 40 years of age with chronic respiratory symptoms as well as one or both of airflow limitation and bronchial hyper-responsiveness (BHR). “Chronic” was defined as symptoms lasting for more than 3 months, or repeated symptoms experienced at intervals of more than 3 months. Respiratory symptoms mainly included cough, phlegm, wheeze, and dyspnea. BHR was measured using the five-breath dosimeter method of the methacholine provocation test, and was defined as the provocative concentration that reduces the FEV1 by 20% below 16 mg/ml; < 1.0 mg/ml defined moderate-to-severe BHR; 1.0–4.0 mg/ml mild BHR (positive test); 4.0–16 mg/ml borderline BHR; above 16 mg/ml normal bronchial responsiveness (dilution using methacholine concentrations of 0.0625, 0.25, 1, 4, and 16 mg/ml) (Citation7). Airway obstruction was diagnosed using the GLI definition of FEV1/FVC < the lower limit of normal (LLN) and z-score, Categorisation of the severity of airway obstruction was made using the five category scale. Mild: z ≥ −2, Moderate: −2 > z ≥ −2.5, Moderately severe: −2.5 > z ≥ −3, Severe: −3 > z ≥ −4, Very severe: −4 > z (Citation8). Unlike other studies, the GIRD Biobank project did not use smoking history as an inclusion criterion. The selection criteria of controls were as follows: Normal spirometry; cancer-free; age between 40–80 years and permanent residents (lived in Guangzhou for years).
Exclusion criteria were the presence of lung disease except asthma (e.g., cystic fibrosis, extensive bronchiectasis, and pulmonary fibrosis), previous surgical excision of at least one lung lobe (or lung volume reduction procedure), active cancer under treatment, suspected lung cancer (large or highly suspicious lung mass), metal in the chest, recent chest or abdominal surgery, recent eye surgery, subjects with recent COPD exacerbations can be enrolled 1 month after their exacerbation, individual history of myocardial infarction, other cardiac hospitalization, inability to use albuterol, history of chest radiation therapy, multiple self-described racial categories, and first or second degree relative already enrolled in the study (Citation6). In addition, pregnant women are also excluded (Citation6). The exclusion criteria of controls were as follows: with cancer; with airflow limitation; age below 40 or above 80; not native. This study is registered with Clinical trial www.chictr.org, number ChiCTR-CCC-12002950.
Data collection, specimen processing, labeling, and storage
The GIRD developed SOP to ensure uniformity in the collection, processing, labeling, and storing of those specimens. Data collection was identical for both COPD patients and control subjects. After obtaining informed, written consent, all participants completed an in-person interview, administered by a trained interviewer.
Data collection
Information collected from each subject using a modified American Thoracic Society (ATS) Respiratory Epidemiology Questionnaire consisted of collecting detailed information on demographic and socioeconomic characteristics, clinical manifestation, anthropometric information, information on individual history of diseases, family history of disease, other co-morbidities, as well as environmental exposures (Citation9). Moreover, we also gathered more information on smoking and drinking habits, education, occupation, indoor living and working environment, physical activity, dietary habits in childhood and adulthood, and menstruation and menarche. Family history of cancer was defined as any self-reported cancer in his/her first-degree relatives (such as parents, siblings, or children).
Longest-held occupation: manual occupations included agricultural worker, factory work, or sales and service; administrator or manager, professional or technical, and military or disciplined were included in mental occupations; high-risk occupations were mainly manual workers involving special type of work such as miners, boiler controller, carpenter, and so on. BMI was calculated as weight divided by height squared. Subjects performed standardized pre-bronchodilator and post-bronchodilator spirometry, using the EasyOne Spirometer (NDD, Inc., Andover, MA) according to ATS/European Respiratory Society criteria (Citation10).
Post-bronchodilator spirometry was performed approximately 20 minutes after administering 180 μg of albuterol via metered dose inhaler. In a few patients who were unable to provide three acceptable maneuvers or slightly exceeded case spirometric criteria, data of these cases were included at the investigators' discretion. Predicted FEV1 percent and FEV1/FVC percent were assessed using the GLI equations (Citation11). And the test result defined by the mean ± SD (strictly 1.96 z-scores), which extends from the 2.5th to the 97.5th centile of the distribution (z-scores indicate how many standard deviations a measurement is from its predicted value).
Extensive information about tobacco smoking was elicited for all participants including all periods of consumption and the number of cigarettes smoked per day. All periods of consumption counted towards total exposure. The definitions of smokers and drinkers have been described previously (Citation12). Inspiratory and expiratory 64-slice spiral CT scanning of the chest was also performed to evaluate the severity and distribution of emphysema as well as the differential diagnosis. The scanning parameters were: 0.723-mm slice thickness, 0.723-mm slice interval, 120 kV voltage, and 276 to 700 mA current (software:Viire®2Version3.7.0.2, Toshiba Corporation, Japan). Characteristics of COPD patients and control subjects with complete data are presented in
Table 1. Demographic characteristics in COPD patients and controls
Specimen processing, labeling, and storing
For each participant, a 10-ml blood specimen was collected into two vacutainers. Blood samples were immediately placed on ice and centrifuged within 2 hours. A blood specimen for DNA was obtained from each subject; serum, plasma, white blood cells, and whole blood were harvested from peripheral blood; each of them was divided into small sizes of 500 microlitres or 100 microlitres in volume, and stored for future biomarker studies. Then, they were loaded into separate Eppendorf tubes marked with individual code number. Eppendorf tubes were sequentially kept in freezing boxes, on the sidewall and the front of which the range of code numbers were labeled. Each code number was linked with a database where demographic, clinical, and specimen-related information were recorded. Other project-specific information was recorded in special charts linked to the inventory. All specimens were stored at the GIRD study in a dedicated −80°C freezer until they were further analyzed (
Figure 1. Structure and information/material flow of the blood-based mainly bank network.
The project was approved by the institutional review boards of Guangzhou Medical University (Ethics Committee of The First Affiliated Hospital: GZMC2009-08-1336) and the Institutional Review Boards of the other hospitals taking part.
Statistical analysis
Baseline characteristics were analyzed for quantitative traits using t-tests and for qualitative traits using the χ2-test or Fisher exact test. The relationships between FEV1% predicted (as dependent variable) and demographic characteristics (as independent variable) were tested by a linear regression model with both univariate model and multivariate model included; Multivariate model was adjusted by age, sex, and smoking (Premove = 0.051 and Penter = 0.05). Effects of demographic characteristics on clinical symptoms were also calculated using stepwise of multivariable logistic regression (Premove = 0.11 and Penter = 0.1 for cough and phlegm; Premove = 0.051 and Penter = 0.05 for wheeze and dyspnea), adjusting for age, sex, and smoking. All analyses were done with Stata software (version 10.0; StataCorp LP, College Station, TX), using two-sided P values.
Spirometry predicted values and z-scores were derived for each subject in each dataset using prediction equations from the Global Lung Function Initiative (GLI-2012) (Citation11), using specially developed GLI-Excel-Calculator in the Supplementary file from the Quanjer et al. study (Citation8).
Results
The data collection and database establishment is ongoing and will continue for years. Since September 2010, a total of 1515 subjects were enrolled. The baseline characteristics of the 855 COPD patients and 660 controls (156 for smoking controls and 504 for non-smoking controls) that were eligible to be included in the analysis, as presented in . Based on the questionnaire and clinical data, the COPD cases and controls did not appear to be matched on age (P < 0.001). All patients were over 40 years (mean age, 69.4 ± 10.0 years). Of these, 728 (85.1%) were male, but the ratio was much lower in controls. Patients were more likely to be male, less educated, consumed slightly more alcohol, and heavy ex-smokers compared to control subjects. In addition, the relationships between COPD patients and controls and other environmental characteristics also were taken. As expected, we found that there were significant differences between the COPD subjects and controls in sources of passive smoking, kitchen fan usage, fuel usage in childhood, X-ray exposure in lifetime, individual history of disease, family history of pulmonary disease, cooking, and lung function (P < 0.05 for all).
Clinical symptoms of COPD cases according to their reported well-known environmental risk factors are shown in . Generally speaking, in the most circumstances, environmental exposures, including smoking, X-ray exposure times in lifetime, fuel usage in childhood, kitchen fan usage, and cooking were significantly associated with anyone reporting of respiratory symptom.
Table 2. Relations between main self-reported environmental risk exposure and respiratory symptoms in subjects with COPD
Then, we evaluated the associations between FEV1% predicted and demographic characteristics in COPD patients by using stepwise of linear regression in . In the univariate model, there were significant differences in age, sex, pack-years, asthma, family history of pulmonary disease, and cooking (P < 0.05 for all). In the multivariable model, adjusted β (S.E.) were −0.45 (0.16) in age (P = 0.004), −0.14 (0.06) in pack-years (P = 0.02), and −2.17 (1.02) in family history of pulmonary disease (P = 0.03). The association between clinical symptoms and demographic characteristics in COPD patients were presented in . After adjusting for age, sex, and smoking, there were significantly differences in age, poisonous exposure, X-ray exposure in lifetime, and vegetable and fruit consumption in cough (Pmax = 0.034); For phlegm, the differences were in age, fuel usage in the recent decade, X-ray exposure in lifetime, cooking, and vegetable and fruit consumption (Pmax = 0.037); For dyspnea, the differences were in sex, pack-years, and family history of pulmonary disease (Pmax = 0.023). In addition, wheeze was associated with many more demographic characteristics in COPD patients.
Table 3. The association between FEV1% predicted and demographic characteristics in COPD patients
Table 4. The association between clinical symptoms and demographic characteristics in COPD patients
In , the first three most influential factors on respiratory symptoms were cold air, haze, and influenza, in both cases and controls. Cases were almost moderately severe or worse, stratified according to GLI (45 for mild, 48 for moderate, 101 for moderately severe, 312 for severe, and 364 for very severe). COPD patients suffered from relatively more co-morbidities than controls such as chronic bronchitis, emphysema, hypertension, heart disease, tuberculosis, bronchiectasis, diabetes, asthma, stroke, and pneumoconiosis. The percentages of mental occupation in COPD were almost the same as manual occupation, and both of them much higher than high-risk occupations, but the majorities of the control were mental occupation. According to , COPD patients had higher “regular” consumptions amount of sauerkraut, pickles, and bacon, compared with controls (P < 0.05). In their childhood, there was a trend towards increased use of coal and wood. However, over the past 10 years, people have preferred to choose clean fuel for cooking and most households used gas rather than coal and wood.
Figure 2. A was percentage of main influential factors on respiratory system in COPD and controls. B was COPD classification% stratified by the criteria of Global Lung Function Initiative (GLI). C was common co-morbidities existing in COPD and controls. D was percentage of the longest held occupation in COPD and controls.
Figure 3. A, B, C, and D were percentages of vegetable and fruit, sauerkraut, pickles foods, and bacon consumption, respectively. E and F were fuel usage in recent 10 years and in childhood.
Discussion
We anticipate that GIRD COPD Biobank will generate a unique, large carefully designed blood-based multicenter observational study in China. In the near future, collections of other biological material (including phlegm, bronchial mucosa, bronchoalveolar lavage, and so on) are also considered. The high level of high-quality characterization will provide a valuable resource for studies concentrating on the genetics, epidemiology, and natural history of COPD. Plans to perform replication studies in more sites and conduct every 6 months' follow-up for various assessments would be expected, so, the project can also be considered a prospective cohort study. Although previous studies have achieved great progress on the study of COPD, we still cannot exclude the need for further studies on COPD (Citation13, 14). From the interim outcomes of the COPD Biobank Study, it showed that the COPD cases and controls did not appear to be matched on age and sex. Therefore, it is necessary to adjust the target populations in the future study.
In the present study, COPD patients more often appeared to be associated with co-morbidities such as bronchiectasis, emphysema, pneumoconiosis, asthma, chronic bronchitis, pulmonary tuberculosis, stroke, heart disease, diabetes, and hypertension compared to controls. Co-morbid conditions in COPD are of importance since they are frequent, affect prognosis and costs of COPD (Citation15–17). COPD patients often present with co-morbid diseases, including cardiovascular disease, metabolic syndrome, osteoporosis, depression, and skeletal muscle wasting and dysfunction (Citation18, Citation19).
COPD is characterized by inflammatory response and vascular remodeling. Systemic inflammation may contribute to the development of co-morbid conditions and these disorders can be seen as manifestations of COPD or vice versa (Citation20). Moreover, since COPD is a kind of age-related disease, accelerated aging is a further process that could account for both the local lung effects of COPD and its co-morbidities (Citation21). Aging is characterized by a progressive, generalized impairment of function, and amplification of the inflammatory response that results in an increased vulnerability to environmental challenge and an increased risk of disease (Citation22). The presence of many of these co-morbidities appears to have a deleterious effect on several outcomes in COPD (Citation23). In particular, diabetes, hypertension, cardiovascular disease, and cancer increase the risk of death in COPD (Citation23). However, whether treatment of co-morbid conditions changes the natural history of COPD or whether treatment of COPD is altered by the presence of a concomitant co-morbidity remains largely unknown and awaits further study.
It is well-recognized that a new insight into the pathogenesis and long-term natural history of COPD can be achieved only through collaborative research conducted in China or international cooperation. Moreover, a better understanding of COPD heterogeneity also requires multinational collaborative research. To our knowledge, it is possible that the GIRD COPD Biobank could cooperate with other biobanks because the GIRD COPD Biobank Project of Southern China was set up in accordance with the international standards. Actually, since 2014, researchers from different regions of China have participated in and recruited more patients in the GIRD COPD project. We believed that undertaking longitudinal studies for longer duration on the COPD patients in China would enable us to discover distinct COPD phenotypes with new therapeutic and prognostic biomarkers. We anticipate that GIRD COPD study will generate a unique, large biobank of well-phenotyped subjects for COPD research. The high level of phenotypic characterization will provide a valuable resource for studies into the genetics, epidemiology, and natural history of COPD.
In addition to the analyses of the entire GIRD COPD Project population listed above, separate analyses of mild cases will also be performed. We will attempt to identify a normal subset and an early disease subgroup within this phenotypic category based on their CT emphysema, CT airway, and spirometric characteristics. The relationship of this “normal” subgroup to functional impairment and disease impact measures will be comprehensively investigated. We hypothesize that individuals in the putative normal subgroup might have less functional impairment, less evidence for disease impact, and fewer exacerbations. Finally, longitudinal follow-up will be required to determine if the hypothesized “normal” subgroup of Mild subjects are less likely to progress to full airflow obstruction. However, cross-sectional analysis of Mild subjects will determine whether clinical heterogeneity can be discerned within these groups using CT data.
COPD is a disease with important public health implications, given its often profound effects on functional capacity, quality of life, and mortality. At this time there is a dearth of effective disease treatments for moderate-to-severe COPD or effective secondary prevention strategies for early COPD persons. Further progress in these areas is hampered by the long latency period such as between smoking exposure and development of clinical disease, as well as by a relatively small proportion of smokers who may develop symptomatic disease. In addition, wide variation in disease expression patterns (airway disease, emphysema, extra-pulmonary effects, patterns of exacerbations, and so on) may limit statistical power to detect successful results within these subsets in therapeutic trials. So, COPD prevention and control has a long way to go.
In conclusion, China's population is undergoing rapid and profound health transitions, and the burden of disease is increasing rapidly. The major risk factors of COPD are out of control if measures and interventions are not taken immediately, and the potential risks become more and more serious. Therefore, the long-term health issues of Chinese people cannot be optimistic. However, the concept of COPD prevention and control is gradually changing, and with more attention given to understanding genetic factors and biomarkers will significantly contribute to earlier diagnosis of this disease and may lead to the development of treatments to modify progression. It is expected to provide new insights into the pathogenesis and the long-term progression of COPD.
Funding
This work was supported by Guangdong Natural Science Foundation Team Grant (1035101200300000), the National Natural Science Foundation of China (81170052, 81070043, 81173112, and 81220108001), the Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme (2014) and the Key Project of Department of Education of Guangdong Province (cxzd1142), a Changjiang Scholars and Innovative Research Team in University Grant (IRT0961), a the Guangdong Department of Science and Technology of China (2009B050700041 and 2010B031600301), a Guangdong Department of Education Research Grant (cxzd1025), Guangzhou Department of Education Yangcheng Scholarships (12A001S), Guangzhou Department of Education Team Grant for Innovation (13C08), and the Municipal Project of Department of Education of Guangzhou (1201430298).
Declaration of Interest Statement
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
Authors Wenju Lu, Zeguang Zheng, Xindong Chen, Hui Tan, Jian Wang, Zili Zhang, Jinping Zheng, and Rongchang Chen contributed equally to this article.
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