Chest
Volume 117, Issue 5, Supplement 2, May 2000, Pages 339S-345S
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Prevalence of Airways Obstruction in a General Population: European Respiratory Society vs American Thoracic Society Definition

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Study objectives

To evaluate the distribution of airways obstruction in a general population sample.

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.

Section snippets

Materials and Methods

Data for these analyses were collected from 1988 to 1991 during the second Po Delta survey (n = 2,841; age, 8 to 73 years), a cross-sectional survey of a longitudinal study carried out to assess the possible effects of a large oil-burning power plant, before and 8 years after its operation, on a general population sample living in Po Delta valley, mostly a lowly polluted rural area.14

The study has been fully described elsewhere.1516171819 Briefly, each subject answered to the

Results

No subject < 14 years old presented airways obstruction by any of the three definitions, while among those 15 to 24 years old (n = 533), there were relatively few people with airways obstruction: 11.7% by ERS criterion, 4.6% by clinical criterion, and 16.3% by ATS criterion. In addition, the proportion of subjects reporting any chronic respiratory symptom was 26%. Thus, the analyses were carried out only in those 25 to 73 years old (n = 1,727). Mean age and values of percent predicted FEV1,

Discussion

The prevalence rate of airways obstruction in the adults of a general population sample living in a lowly polluted rural area of North Italy varies, according to the criterion used for its definition, from 11.0% with ERS to 18.3% with the clinical criterion, up to 40.4% with the ATS criterion.

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

Conclusion

Our findings show that the prevalence of COPD in a general population depends very much on the criterion used for airways obstruction definition, and that no existing criterion, neither recommended by scientific societies nor clinically chosen, is epidemiologically consistent. Thus, further research is needed to reach a common standardized and valid criterion for the definition of airways obstruction.

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    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.

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