| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Guest Access | Sign In via User Name/Password
|
|
|
|||||||
Guest Access | Sign In via User Name/Password |
|||||||||
* From the CNR Institute of Clinical Physiology (Drs. Viegi, Pedreschi, and Ms. Baldacci), Pulmonary Environmental Epidemiology Group Pisa; and Cardiopulmonary Department (Drs. Pistelli, Carrozzi, Giuntini, and Mr. DiPede), University and Hospital of Pisa, Italy.
Correspondence to: Giovanni Viegi, MD, CNR Institute of Clinical Physiology, Via Trieste 41, 56126 Pisa, Italy; e-mail: viegig{at}ifc.pi.cnr.it
 |
Abstract |
|---|
 TOP Abstract IntroductionMaterials and MethodsResultsDiscussionConclusionReferences |
|---|
Methods: Cross-sectional epidemiologic survey of a general population sample living in Po Delta area (North Italy). Data on respiratory symptoms, diseases, and risk factors were collected through standardized interviewer-administered questionnaires. Lung function tests were performed, with criteria for defining airways obstruction based on the 1995 European Respiratory Society (ERS) statement (FEV1/vital capacity ratio < 88% predicted and < 89% predicted in men and women, respectively), "clinical" criteria (FEV1/FVC ratio < 70%), and the 1986 American Thoracic Society (ATS) statement (FEV1/FVC ratio < 75%).
Results: A total of 1,727 subjects aged > 25 years
investigated from 1988 to 1991 were included. Prevalence rates of
airways obstruction for subjects 25 to 45 years old and subjects 
46
years old were as follows: ERS, 10.8% and 12.2%; clinical, 9.9% and
28.8%; and ATS, 27% and 57%, respectively. When considering only
moderate/severe obstruction, the rates were as follows: ERS, 0.4% and
3.6%; clinical, 0.3% and 4.4%; and ATS, 0.5% and 5.2%,
respectively. The trend was confirmed after stratifying for smoking
habit and the presence/absence of respiratory symptoms/diseases. The
highest specificity and predictive value for any respiratory
symptom/disease was shown by the ERS, and the lowest was shown by the
ATS criterion, while the reverse was true for sensitivity; overall
accuracy was slightly lower for the ATS criterion. Multiple logistic
regression models indicated a higher number of significant associations
with known risk factors for airways obstruction according to clinical
and ATS criteria than ERS criterion.
Conclusions: The prevalence of COPD in a general population depends very much on the criterion used for definition of airways obstruction. Further research is needed to reach a standardized and epidemiologically consistent criterion for airways obstruction.
Key Words: airways obstruction definition • COPD • epidemiological survey • FEV1 • FVC • general population • prevalence
|
Introduction |
|---|
|
TOPAbstractIntroductionMaterials and MethodsResultsDiscussionConclusionReferences |
|---|
An important difference between the two documents is represented by the definition of airways obstruction. The ERS document2 states that airways obstruction is present when the FEV1/slow vital capacity (VC) ratio is < 88% of the predicted value in men and < 89% predicted in women; subsequently, severity of COPD is graded on the level of reduction of percent predicted FEV1. Conversely, in the ATS document,1 the presence of airways obstruction is not numerically defined, with only the grade of COPD severity detailed. Indeed, although the practice of defining a fixed FEV1/FVC ratio as a lower limit of normal was not recommended in the 1991 ATS document,5 only in an ATS document of > 10 years ago6 is a precise definition of airways obstruction indicated (as a FEV1/FVC ratio < 75%), and this is still in use.
In clinical activities in Europe, an empirical level of 70% for FEV1/FVC is often used to define airways obstruction. The issue of an accurate definition of COPD is critical in epidemiology in order to compare findings of different surveys,7 8 9 10 but it is also important for clinical studies assessing survival11 or lung function outcomes.12 13
The aim of this study is to evaluate the distribution of COPD in terms of prevalence and severity by comparing the ERS and the ATS criteria, along with the "clinical" one, in a general population sample living in a lowly polluted area of North Italy.
|
Materials and Methods |
|---|
|
TOPAbstractIntroductionMaterials and MethodsResultsDiscussionConclusionReferences |
|---|
The study has been fully described elsewhere.15 16 17 18 19 Briefly, each subject answered to the interviewer-administered standardized questionnaire on respiratory symptoms, diseases, and risk factors, elaborated by the Italian National Research Council based on that of the National Heart, Lung, and Blood Institute.16 Subjects were also invited to undergo objective methods of investigation, including VC and forced expirograms.
A computerized pneumotachograph (Pulmonary System 47804S; Hewlett-Packard; Waltham, MA) was used for the acquisition and on-line analysis of lung function data during the field survey. The system consisted of a Fleisch pneumotachograph No. 3, for flow measurements, linked via an analog-to-digital converter (47310A; Hewlett-Packard) to a 9825A calculator (Hewlett-Packard; Cupertino, CA). In this system, the pressure change, induced by the respiratory flow passing through the pneumotachograph, was translated into millivolts. The analog-to-digital converter translated measured millivolts to digits, and the computer integrated the volume signal from the flow signal. The pneumotachograph response was linear (± 3% between 1 and 12 L/s). The end point of the FVC maneuver was determined using feedback requiring consecutive samples to determine a flow < 15 mL/s, and no time limitation was imposed by the algorithm.20 The volume calibration of the pneumotachograph was performed daily with a 3.0-L standard syringe. Each subject performed at least three acceptable and reproducible FVC maneuvers, as specified by ATS protocol.21 Predicted values were computed using reference equations derived from normal subjects within the sample that took part in the first cross-sectional investigation in the Po Delta area.17
Definition of COPD was made according to the following criteria: ERS,
FEV1/VC < 88% predicted in men or < 89%
predicted in women2
; "clinical,"
FEV1/FVC < 70%; and ATS,
FEV1/FVC < 75%.6
Severity of COPD
was defined as follows: ERS, mild (FEV1 70%
predicted), moderate (FEV1 69 to 50% predicted),
or severe (FEV1 < 50%
predicted)2
; clinical, mild (FEV1
70% predicted), or moderate-severe (FEV1
< 70% predicted); and ATS, mild (FEV1 100 to
70% predicted), moderate (FEV1 69 to 60%
predicted), moderately severe (FEV1 59 to 50%
predicted), severe (FEV1 49 to 34% predicted),
or very severe (FEV1 < 34%
predicted).21
With the ATS severity grading, mild,
moderate, and moderately severe levels would correspond to COPD stage
I, severe level to COPD stage II, and very severe level to COPD stage
III.1
Subjects were considered symptomatic if they answered affirmatively to any question referring to chronic respiratory symptoms and/or diseases. In addition, subjects who reported wheeze or a medical diagnosis of asthma were considered in the analyses. Subjects who answered affirmatively to standard questions regarding chronic cough, chronic phlegm, or a diagnosis of chronic bronchitis and/or pulmonary emphysema were defined as suffering from chronic obstructive lung disease. Another category was made by those reporting dyspnea on exertion.
Nonsmokers were defined as those who never had smoked. Smokers were
those who were currently smoking at least one cigarette daily.
Ex-smokers included those who had formerly smoked regularly until 6
months before the examination.
In the logistic regression models, the following risk factors for airways obstruction were analyzed: age; height; weight; pack-years; familial history for COPD; childhood respiratory infections; work exposure to dusts/chemicals; and low socioeconomic conditions. Age was expressed in decades, height was expressed in decimeters, and weight was expressed in kilograms. Pack-years (ie, number of cigarettes smoked daily multiplied by the years of smoking divided by 20) was multiplied by 10. Childhood respiratory infections were based on whether the subject had frequent chest colds, and one or more episodes of pneumonia, croup, or pseudocroup before the age of 12 years. Low socioeconomic condition was determined on the basis of two indexes: crowding (the number of subjects living in the house divided by the number of rooms), and occupation (the percentage of those in higher occupational positions based on the official classification of the National Statistics Institute, ie, white-collar workers, self-employed, professionals, and managers). In particular, low socioeconomic conditions were characterized by the position of the subject in the upper tertile of the frequency distribution of crowding, and in the lower tertile of the frequency distribution of occupation.
Statistical analyses were performed at the Pisa University Computer
Center using the Statistical Package for the Social Sciences (SPSSX;
SPSS; Chicago, IL). The following analyses were applied: frequency
distribution, 
2 test, one-way analysis of
variance, and multiple logistic regression.
Sensitivity, specificity, predictive value, and overall accuracy22 of each criterion of COPD definition were assessed on the basis of presence/absence of any chronic respiratory symptom/disease.
|
Results |
|---|
|
TOPAbstractIntroductionMaterials and MethodsResultsDiscussionConclusionReferences |
|---|
|
|
46 years
old, smokers showed the largest prevalence rates of airways obstruction
for all criteria, followed by ex-smokers, with the exception of male
subjects for the ERS definition. Almost all the pair comparisons (ERS
vs ATS, ERS vs clinical, and clinical vs ATS) were significantly
different by 2 tests. A nonsignificant
comparison was observed for nonsmoking men (ERS vs ATS) in subjects
46 years old, and borderline comparisons were noted in the
ex-smoker and nonsmoker female subjects (ERS vs ATS), also in subjects
46 years old.
|
|
Multiple logistic regression analyses were performed in order to evaluate the determinants for the presence of airways obstruction by each criterion (Table 5 ). Lifetime cigarette consumption (expressed as pack-years) and childhood respiratory infections were significant risk factors for airways obstruction in both sexes according to all three criteria (except for ATS in female subjects with regard to childhood respiratory infections). Familial history for COPD was a significant risk factor in male subjects for ATS and clinical criteria, and in female subjects for ERS criterion (in the opposite direction). Age and height were significant risk factors according to both clinical and ATS criteria, but not according to ERS criterion. Work exposure to dusts/chemicals was significantly associated with airways obstruction for ATS criterion in male subjects and for clinical criterion in female subjects (in the opposite direction). Low socioeconomic condition was significantly associated with airway obstruction for ATS criterion in male subjects. Weight, familial history for asthma, and adolescence-adulthood respiratory infections did not show any significant association.
|
|
Discussion |
|---|
|
TOPAbstractIntroductionMaterials and MethodsResultsDiscussionConclusionReferences |
|---|
The ATS criterion shows an overestimation of the prevalence of COPD, in
so far as the threshold FEV1/FVC ratio for
considering the presence of airways obstruction is at a very high
level.6
In the 1991 ATS statement on the interpretative
strategies of lung function testing,5
an obstructive
ventilatory defect was defined on the basis of the reduction of
FEV1/VC, without recommending a definite value
for diagnosing it. Moreover, in two more recent ATS documents dealing
with airways obstruction,1
23
it was not clearly stated
when airways obstruction is present. Therefore, the 1986
criterion,5
which is still in use, was used in these
analyses. The overestimation of airways obstruction prevalence occurs
especially for the mild level with the ATS criterion, particularly in
subjects 46 years old. This trend is present also when stratifying
subjects by smoking status, or considering separately subjects without
respiratory symptoms and subjects with symptoms/diagnosis of chronic
bronchitis or emphysema and of asthma, or wheeze (ie, a
symptom that may be present in either disease).
The ERS criterion of defining and grading COPD severity is theoretically reliable, since it takes into account the physiologic reduction of airway caliber with aging.19 On the other hand, the ERS criterion yields lower sensitivity (17%) and higher specificity and positive predicted value (93% and 58%) than both the ATS and the clinical criteria, and similar values of negative predicted value. The overall accuracy is equal for ERS and clinical criterion (64%), and higher than that of the ATS (58%). Hence, the overall accuracy of the diagnosis of COPD is, at present, rather limited. Further, no actual criterion of defining airways obstruction appears to be epidemiologically valid, at least in a general population sample characterized by a low prevalence rate of diseased subjects. These results are certainly influenced by the choice of such reported symptoms/diseases as a "gold standard" for validation of the COPD definition, since reported symptoms/diseases are scanty until the disease process is fairly advanced. However, this is an unavoidable issue in epidemiologic studies in which no direct medical evaluation or other tests (radiography, CT scan) are available.
Concerning the comparison of the prevalence rates of airways obstruction in different populations, the figures range from 0.8 to 13.2% in US studies.24 Lebowitz25 reported prevalence rates of physician-confirmed airways obstructive disease (emphysema, chronic bronchitis, or asthma) with an FEV1/FVC ratio < 75% in the general population sample of Tucson, AZ, in individuals aged 25 to 75 years; values ranged from 8 to 21% in men and from 9 to 24% in women. Beside the variance due to the characteristics of the different populations, there is a variance due to the lack of a standardized definition of airways obstruction.
With regard to the degree of severity of airways obstruction, our data show that, in a general population living in a lowly area exposed to air pollution, there are very few subjects with moderate/severe airways obstruction. One might consider that this is due to a sort of "healthy worker" effect, ie, that people with a severe disease die earlier or that they are not willing to participate in an epidemiologic study. As far as the latter issue is concerned, however, data collected by others in a different study26 show that the reverse is true, ie, people with symptoms or disease tend to participate more frequently in an epidemiologic study.
The results of logistic regression analyses confirm that important differences exist between ERS criterion and the ATS and clinical criteria. In fact, while only pack-years and childhood respiratory infections diseases are consolidated risk factors for airways obstruction according to ERS criterion, more risk factors are significantly associated with the presence of airways obstruction according to ATS and clinical criteria. These findings are in line with those obtained in the first Po Delta study,18 and might indicate that ATS and clinical criteria identify subjects with an early stage of airways obstruction. They, with the exception of the elderly, can benefit from the removal of risk factors such as smoking, occupational exposure to dusts, chemicals, or fumes, and low socioeconomic condition. Conversely, the ERS criterion would seem to identify subjects who have an established airways obstruction because they have smoked too much and have already had childhood respiratory infections.
In order to extend the process of standardization in a global view of respiratory medicine, as also discussed in the 1997 ATS Planning Retreat (personal notes; April 24–25, 1997), a common definition of airways obstruction would be desirable. From this point of view, the ATS document of 19915 and especially that of 19951 are helpful in so far as they have recommended the use of slow VC, ie, one of the essential factors to define airways obstruction according to the ERS criterion.2 Since the goal is to achieve a test that has a good sensitivity, specificity, predictive value, and overall accuracy, ad hoc clinical and epidemiologic studies might be needed.
The importance of the definition of airways obstruction is highlighted in the guidelines on COPD management issued by other scientific societies. The Canadian Thoracic Society27 did not provide any functional level to define airways obstruction, whereas the Thoracic Society of Australia and New Zealand28 reported two different figures for FEV1/VC (< 70%) and FEV1/FVC (< 75%). Finally, the British Thoracic Society29 required the presence of both a reduced FEV1 (< 80% predicted) and an FEV1/VC ratio of < 70% to diagnose airways obstruction. Even the graduation of COPD severity based on percent predicted FEV1 levels was different from those proposed by ATS and ERS.
|
Conclusion |
|---|
|
TOPAbstractIntroductionMaterials and MethodsResultsDiscussionConclusionReferences |
|---|
|
Footnotes |
|---|
This study was supported in part by the Italian National Research Council, Targeted Project "Prevention and Control Disease Factors-SP 2" (Contract 91.00171.PF41), by Contract 587-1997 with Ministero del Lavoro e della Previdenza Sociale, and by an educational grant from Smithkline Beecham, Collegeville, PA.
|
References |
|---|
|
TOPAbstractIntroductionMaterials and MethodsResultsDiscussionConclusionReferences |
|---|
This article has been cited by other articles:
|
|
 |
|
  Y.-C. Wang, J.-M. Lin, C.-Y. Li, L.-T. Lee, Y.-L. Guo, and F.-C. Sung Prevalence and Risks of Chronic Airway Obstruction: A Population Cohort Study in Taiwan Chest, March 1, 2007; 131(3): 705 - 710. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Pelkonen, I.-L. Notkola, A. Nissinen, H. Tukiainen, and H. Koskela Thirty-Year Cumulative Incidence of Chronic Bronchitis and COPD in Relation to 30-Year Pulmonary Function and 40-Year Mortality: A Follow-up in Middle-Aged Rural Men. Chest, October 1, 2006; 130(4): 1129 - 1137. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. M. G. Halpin and M. Miravitlles Chronic Obstructive Pulmonary Disease: The Disease and Its Burden to Society Proceedings of the ATS, September 1, 2006; 3(7): 619 - 623. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. J. Halbert, J. L. Natoli, A. Gano, E. Badamgarav, A. S. Buist, and D. M. Mannino Global burden of COPD: systematic review and meta-analysis Eur. Respir. J., September 1, 2006; 28(3): 523 - 532. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Zielinski, M. Bednarek, D. Gorecka, G. Viegi, S. S. Hurd, Y. Fukuchi, C. K. W. Lai, P. X. Ran, F. W. S. Ko, S. M. Liu, et al. Increasing COPD awareness. Eur. Respir. J., April 1, 2006; 27(4): 833 - 852. [Full Text] [PDF]
|
|
|
|
 |
|
 D. S. Kim, Y. S. Kim, K.-S. Jung, J. H. Chang, C.-M. Lim, J. H. Lee, S.-T. Uh, J. J. Shim, W. J. Lew, and on behalf of the Korean Academy of Tuberculosis an Prevalence of Chronic Obstructive Pulmonary Disease in Korea: A Population-based Spirometry Survey Am. J. Respir. Crit. Care Med., October 1, 2005; 172(7): 842 - 847. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. M. Geijer, A. P. Sachs, A. W Hoes, P. L Salome, J.-W. J Lammers, and T. J. Verheij Prevalence of undetected persistent airflow obstruction in male smokers 40-65 years old Fam. Pract., October 1, 2005; 22(5): 485 - 489. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Lin, Y. Chen, and I. McDowell Increased risk of depression in COPD patients with higher education and income Chronic Respiratory Disease, January 1, 2005; 2(1): 13 - 19. [Abstract] [PDF]
|
|
|
|
|
|
C. Shin, S. Lee, R. D. Abbott, J. H. Kim, S. Y. Lee, K. H. In, and K. Kimm Respiratory Symptoms and Undiagnosed Airflow Obstruction in Middle-Aged Adults: The Korean Health and Genome Study Chest, October 1, 2004; 126(4): 1234 - 1240. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. A. M. Kerstjens The GOLD Classification Has Not Advanced Understanding of COPD Am. J. Respir. Crit. Care Med., August 1, 2004; 170(3): 212 - 213. [Full Text] [PDF]
|
|
|
|
|
|
C. Shin, K. H. In, J. J. Shim, S. H. Yoo, K. H. Kang, M. Hong, and K. Choi Prevalence and Correlates of Airway Obstruction in a Community-Based Sample of Adults Chest, June 1, 2003; 123(6): 1924 - 1931. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S.T. Weiss, D.L. DeMeo, and D.S. Postma COPD: problems in diagnosis and measurement Eur. Respir. J., June 1, 2003; 21(41_suppl): 4S - 12s. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. J. Halbert, S. Isonaka, D. George, and A. Iqbal Interpreting COPD Prevalence Estimates: What Is the True Burden of Disease? Chest, May 1, 2003; 123(5): 1684 - 1692. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Lundback, A. Gulsvik, M. Albers, P. Bakke, E. Ronmark, G. van den Boom, J. Brogger, L-G. Larsson, I. Welle, C. van Weel, et al. Epidemiological aspects and early detection of chronic obstructive airway diseases in the elderly Eur. Respir. J., May 1, 2003; 21(40_suppl): 3S - 9s. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Sandstrom, A.J. Frew, M. Svartengren, and G. Viegi The need for a focus on air pollution research in the elderly Eur. Respir. J., May 1, 2003; 21(40_suppl): 92S - 95s. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
