Prevalence of airways obstruction in a general population - European Respiratory Society vs American Thoracic Society definition

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 greater than or equal to 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.