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Respiration. 2011;82(1):19-27. doi: 10.1159/000323075. Epub 2011 Jan 29.

Asthma masquerading as chronic obstructive pulmonary disease: a study of smokers fulfilling the GOLD definition of chronic obstructive pulmonary disease.

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  • 1Department of Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia. falkassimi @ yahoo.com

Abstract

BACKGROUND:

Irreversible airways obstruction in smokers is usually attributed to chronic obstructive pulmonary disease (COPD). We speculate that some of these are cases of asthma indistinguishable from COPD.

OBJECTIVES:

To determine the prevalence of asthma in a 'COPD' population and how to differentiate the two conditions.

METHODS:

This was a prospective observational study of smokers fulfilling the Global Initiative for Chronic Obstructive Lung Disease definition of COPD [mean post-salbutamol forced expiratory volume in 1 s (FEV1) 66.9% predicted]. They were classified into 4 groups, as follows: (1) inhaled corticosteroid (ICS)-responsive asthma, defined by normalization of spirometry upon ICS treatment; (2) irreversible asthma, defined as airway obstruction for 1 year and bronchial biopsy indicating asthma; (3) COPD, in the presence of bilateral panlobular emphysema with bullae on high-resolution computed tomography, hypercapneic respiratory failure or bronchial biopsy indicating COPD, and (4) unclassified airflow limitation (AFL).

RESULTS:

Eighty patients fulfilled the definition of COPD. The initial diagnosis was COPD in 57.5% and asthma in 42.5%. The final diagnosis was ICS-responsive asthma in 48 patients (60%), irreversible asthma in 8 (10%), COPD in 16 (20%) and unclassified AFL in 8 (10%). A normal transfer coefficient for carbon monoxide (KCO) and an FEV1 fluctuation ≥18% during 1 year of follow-up distinguished irreversible asthma and COPD. Seven of the 8 patients with irreversible asthma had improved FEV1 at the end of 1 year (median 320 ml compared with -29 ml in COPD). Five out of the 8 unclassified AFL cases had normal KCO and a large improvement in FEV(1) suggestive of irreversible asthma.

CONCLUSIONS:

COPD, even in heavy smokers, includes cases of asthma. FEV1 fluctuation during 1 year is a novel concept which may distinguish irreversible asthma and COPD.

Copyright © 2011 S. Karger AG, Basel.

[PubMed - indexed for MEDLINE]
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