Background: The current debate about the lower limit of normal (LLN) vs the 0.7 fixed ratio to diagnose COPD is not completely resolved, and little information about the clinical impact of these different criteria is available. We compared differences in health-related quality of life, exacerbations, exercise tolerance, physical activity, comorbidity, and systemic biomarkers of subjects with FEV(1)/FVC < 0.7 but > LLN (ratio-only group) vs subjects without COPD and those with mild or moderate to severe COPD.
Methods: A population-based sample of 3,802 subjects aged 40 to 80 years from the Epidemiologic Study of COPD in Spain was selected. Subjects were evaluated with postbronchodilator spirometry, quality-of-life and physical activity questionnaires, and 6-min walk tests. Exacerbations within the previous year and comorbidities were recorded. Systemic biomarkers were measured after excluding subjects with conditions associated with systemic inflammatory processes.
Results: Fixed-ratio COPD overdiagnosis affects up to 4.6% of subjects aged 40 to 80 years, is more frequent in men, and increases with age. After adjusting for confounding factors, the ratio-only group had a worse health-related quality of life than the non-COPD group, with poorer scores in all questionnaire domains (P < .05). However, no differences between the two groups for respiratory exacerbations, 6-min walk distance, physical activity, or systemic biomarkers were observed. Ratio-only subjects did not present greater risk for cardiovascular disease (adjusted relative OR, 1.47; 95% CI, 0.81-2.64), whereas subjects with mild COPD did (adjusted relative OR, 2.32; 95% CI, 1.11-4.84).
Conclusions: Subjects receiving a diagnosis of COPD by the fixed ratio present worse self-reported quality of life than subjects without COPD but had similar exercise, frequency of exacerbations, and indices of systemic effects.