Asthma and COPD Overlap Syndrome (ACOS)

Abstract Asthma and chronic obstructive pulmonary disease (COPD) have traditionally been viewed as distinct clinical entities. Recently, however, much attention has been focused on patients with overlapping features of both asthma and COPD: those with asthma COPD overlap syndrome (ACOS). A significant proportion of patients who present with symptoms of a chronic airways disease have features of both asthma and COPD. Several diagnostic terms, most including the word “overlap”, have been applied to such patients, and the topic has been extensively reviewed. However, there is no generally agreed term or defining features for this category of chronic airflow limitation, although a definition based upon consensus has been published for overlap in patients with existing COPD. In spite of these uncertainties, there is broad agreement that patients with features of both asthma and COPD experience frequent exacerbations, have poor quality of life, a more rapid decline in lung function and high mortality, and consume a disproportionate amount of healthcare resources than asthma or COPD alone. ACOS accounts for approximately 15-25% of the obstructive airway diseases and patients experience worse outcomes compared to asthma or COPD alone. Patients with ACOS often have the combined risk factors of smoking and atopy, are generally younger than patients with COPD and experience acute exacerbations with higher frequency and greater severity than in COPD alone. Pharmacotherapeutic considerations require an integrated approach, first to identify the relevant clinical phenoltype( s), then to determine the best available therapy. The authors discuss the array of existing and emerging classes of drugs which patients with ACOS could benefit from and share their therapeutic approach. A consensus international definition of ACOS is needed to design prospective. Randomized clinical trials are necessary to evaluate specific influence of drug interventions on important outcomes such as lung function, acute exacerbations, quality of life and mortality.