Predictive value of lung function below the normal range and respiratory symptoms for progression of chronic obstructive pulmonary disease

Background: Chronic obstructive pulmonary disease ( COPD) is an insidiously starting disease. Early detection has high priority because of the possibility of early implementation of smoking cessation interventions. An evidence based model for case finding of COPD is not yet available. Objective: To describe the early development of COPD, and to assess the predictive value of early signs (respiratory symptoms, lung function below the normal range, reversibility). Design and methods: In a prospective study, based in general practice, formerly undiagnosed subjects (n = 464) were assessed at baseline and at 5 years for respiratory symptoms and pulmonary function. Odds ratios for early signs were calculated ( adjusted for age, gender, pack-years at baseline and smoking behaviour during follow-up), and defined as possible indicators of disease progression. Results: Over a 5 year period, the percentage of subjects with obstruction increased from 7.5% (n = 35) at baseline to 24.8% (n = 115) at 5 years. The presence of mild early signs and lung function below the normal range at baseline were related to an increased risk of developing mild to moderate COPD (GOLD I: OR 1.87 (95% CI 1.22 to 2.87); GOLD II: OR 2.08 (95% CI 1.29 to 3.37) to 2.54 (95% CI 1.25 to 5.19)) at 5 years. Conclusion: Lung function below the normal range and early respiratory signs predict the development and progression of COPD.