Abstract
OBJECTIVES: To evaluate whether a novel definition of spirometric respiratory impairment from the Global Lung Initiative (GLI) is strongly associated with respiratory symptoms and, in turn, frequently establishes symptomatic respiratory disease. DESIGN: Cross-sectional. SETTING: Third National Health and Nutrition Examination Survey. PARTICIPANTS: Community-dwelling individuals aged 40 to 80 (N = 7,115). MEASUREMENTS: GLI-defined spirometric respiratory impairment (airflow obstruction and restrictive pattern), dyspnea on exertion (DOE), chronic bronchitis (CB), and wheezing. RESULTS: Prevalence rates were 12.7% for airflow obstruction, 6.2% for restrictive pattern, 28.6% for DOE, 12.6% for CB, and 12.9% for wheezing. Airflow obstruction was associated with DOE (adjusted odds ratio (aOR) = 1.69, 95% confidence interval (CI) = 1.42-2.02), CB (aOR = 1.92, 95% CI = 1.62-2.29), and wheezing (aOR = 2.50, 95% CI = 2.08-3.00), and restrictive pattern was associated with DOE (aOR = 1.75, 95% CI = 1.36-2.25), CB (aOR = 1.39, 95% CI = 1.08-1.78), and wheezing (aOR = 1.53, 95% CI = 1.15-2.04). Nonetheless, among participants who had airflow obstruction and restrictive pattern, only a minority had DOE (38.6% and 45.5%), CB (23.3% and 15.9%), and wheezing (24.4% and 19.1%), yielding a positive predictive value (PPV) of only 53% for any respiratory symptom in the setting of any spirometric respiratory impairment. In addition, most participants who had DOE (73.0%), CB (67.8%), and wheezing (66.8%) did not have airflow obstruction or restrictive pattern, yielding a PPV of only 26% for any spirometric respiratory impairment in the setting of any respiratory symptom. The results differed only modestly when stratified according to age (40-64 vs 65-80). CONCLUSION: GLI-defined spirometric respiratory impairment increased the likelihood of respiratory symptoms but was nonetheless a poor predictor of respiratory symptoms. Similarly, respiratory symptoms were poor predictors of GLI-defined spirometric respiratory impairment. Hence, a comprehensive assessment is needed when evaluating respiratory symptoms, even in the presence of spirometric respiratory impairment.