Phenotype of asthma-chronic obstructive pulmonary disease overlap syndrome

Abstract

Many patients with asthma or chronic obstructive pulmonary disease (COPD) have overlapping characteristics of both diseases. By spirometric definition, patients with both fixed airflow obstruction (AO) and bronchodilator reversibility or fixed AO and bronchial hyperresponsiveness can be considered to have asthma-COPD overlap syndrome (ACOS). However, patients regarded to have ACOS by spirometric criteria alone are heterogeneous and can be classified by phenotype. Eosinophilic inflammation, a history of allergic disease, and smoke exposure are important components in the classification of ACOS. Each phenotype has a different underlying pathophysiology, set of characteristics, and prognosis. Medical treatment for ACOS should be tailored according to phenotype. A narrower definition of ACOS that includes both spirometric and clinical criteria is needed.

Keywords: Asthma; Phenotype; Pulmonary disease, chronic obstructive.

Figure 1. Definition of asthma-chronic obstructive pulmonary disease (COPD) overlap syndrome (ACOS) by spirometric criteria. Patients with irreversible airf low obstruction (AO) + bronchodilator reversibility (BDR) or irreversible AO + bronchial hyperresponsiveness (BHR) can be considered to have ACOS. Modified from Gibson and Simpson [1]. FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity.

Figure 2. Phenotypes of asthma-chronic obstructive pulmonary disease (COPD) overlap syndrome.

Figure 3. Clinical characteristics of asthma-chronic obstructive pulmonary disease (COPD) overlap syndrome according to phenotype.

Figure 4. Percentage of patients diagnosed with asthma-chronic obstructive pulmonary disease (COPD) overlap syndrome (ACOS) in different age groups. The percentage of ACOS increases with age. Adapted from Lee et al. [9] according to the Creative Commons License of Yonsei Med J.

Figure 5. Percentage of sputum eosinophils in the groups. The percentage of sputum eosinophils was signif icantly higher in the asthma-chronic obstructive pulmonary disease (COPD) overlap syndrome (ACOS) group. Iwamoto et al. [14] compared the sputum eosinophil concentration in five groups. Kitaguchi et al. [15] compared this concentration in two groups. Modified from Iwamoto et al. [14] and Kitaguchi et al. [15]. ^ap < 0.05 compared with nonsmokers, healthy smokers, and COPD only. ^bp < 0.05 compared with COPD only.

Figure 6. Treatment options for asthma-chronic obstructive pulmonary disease (COPD) overlap syndrome according to phenotype. ICS, inhaled corticosteroid; LABA, long-acting beta agonist; LAMA, long-acting muscarinic antagonist; LTRA, leukotriene antagonist; IgE, immunoglobulin E; PDE4I, phosphodiesterase 4 inhibitor.

Figure 7. Suggested narrow definition of asthma-chronic obstructive pulmonary disease (COPD) overlap syndrome (ACOS). Patients who meet all four criteria can be considered as having ACOS. This definition is well compatible with phenotype C. FE_NO, fractional exhaled nitric oxide; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity.