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 (FEV(1)/vital capacity ratio < 88% predicted and < 89% predicted in men and women, respectively), "clinical" criteria (FEV(1)/FVC ratio < 70%), and the 1986 American Thoracic Society (ATS) statement (FEV(1)/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.