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

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


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.

MeSH terms

  • Adult
  • Aged
  • Asthma / complications
  • Asthma / diagnosis*
  • Asthma / epidemiology
  • Asthma / pathology
  • Asthma / physiopathology
  • Diagnosis, Differential
  • Female
  • Forced Expiratory Volume
  • Humans
  • Male
  • Middle Aged
  • Prevalence
  • Prospective Studies
  • Pulmonary Disease, Chronic Obstructive / complications
  • Pulmonary Disease, Chronic Obstructive / diagnosis*
  • Smoking*
  • Spirometry
  • Vital Capacity