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Quantitative Computed Tomography Measures of Emphysema and Airway Wall Thickness Are Related to Respiratory Symptoms

¹ Department of Thoracic Medicine, Haukeland University Hospital and ² Institute of Medicine, University of Bergen, Bergen, Norway; ³ Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark; ⁴ Department of Radiology and James Hogg iCAPTURE Centre for Cardiovascular and Pulmonary Research, University of British Columbia, Vancouver, British Columbia, Canada; ⁵ Division of Physiology, Department of Medicine, University of California San Diego, San Diego, California; ⁶ Department of Occupational Medicine, Haukeland University Hospital, Bergen, Norway; ⁷ Pharmaceutical Exploratory Development, Hoffman-La Roche, Nutley, New Jersey; ⁸ Research and Development, GlaxoSmithKline, Research Triangle Park, North Carolina; ⁹ Center for Clinical Research, Haukeland University Hospital and ¹⁰ Research Group on Lifestyle Epidemiology, Department of Public Health and Primary Care, University of Bergen, Bergen, Norway

Correspondence and requests for reprints should be addressed to Thomas Grydeland, M.D., Department of Thoracic Medicine, Haukeland University Hospital, N-5021 Bergen, Norway. E-mail: thomas.grydeland{at}med.uib.no

Rationale: There is limited knowledge about the relationship between respiratory symptoms and quantitative high-resolution computed tomography measures of emphysema and airway wall thickness.

Objectives: To describe the ability of these measures of emphysema and airway wall thickness to predict respiratory symptoms in subjects with and without chronic obstructive pulmonary disease (COPD).

Methods: We included 463 subjects with chronic obstructive pulmonary disease (COPD) (65% men) and 488 subjects without COPD (53% men). All subjects were current or ex-smokers older than 40 years. They underwent spirometry and high-resolution computed tomography examination, and completed an American Thoracic Society questionnaire on respiratory symptoms.

Measurements and Main Results: Median (25th percentile, 75th percentile) percent low-attenuation areas less than –950 Hounsfield units (%LAA) was 7.0 (2.2, 17.8) in subjects with COPD and 0.5 (0.2, 1.3) in subjects without COPD. Mean (SD) standardized airway wall thickness (AWT) at an internal perimeter of 10 mm (AWT-Pi10) was 4.94 (0.33) mm in subjects with COPD and 4.77 (0.29) in subjects without COPD. Both %LAA and AWT-Pi10 were independently and significantly related to the level of dyspnea among subjects with COPD, even after adjustments for percent predicted FEV₁. AWT-Pi10 was significantly related to cough and wheezing in subjects with COPD, and to wheezing in subjects without COPD. Odds ratios (95% confidence intervals) for increased dyspnea in subjects with COPD and in subjects without COPD were 1.9 (1.5–2.3) and 1.9 (0.6–6.6) per 10% increase in %LAA, and 1.07 (1.01–1.14) and 1.11 (0.99–1.24) per 0.1-mm increase in AWT-Pi10, respectively.

Conclusions: Quantitative computed tomography assessment of the lung parenchyma and airways may be used to explain the presence of respiratory symptoms beyond the information offered by spirometry.

Key Words: chronic obstructive pulmonary disease • computed tomography • dyspnea • cough • wheezing

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject There is limited knowledge about the association between respiratory symptoms and quantitative computed tomography (CT) measures of emphysema and airway wall thickness. What This Study Adds to the Field Quantitative CT measures of emphysema and airways may be used to explain the presence of respiratory symptoms in subjects with chronic obstructive pulmonary disease beyond the information available from spirometry alone. Level of dyspnea was predicted by quantitative CT measures of both emphysema and airway wall thickness, whereas the presence of coughing and wheezing was best predicted by airway wall thickness. There were only small sex differences.