Does Asthma-COPD Overlap Syndrome (ACOS) exist as a recognized clinical entity?

From the Guidelines

Yes, Asthma-COPD Overlap Syndrome (ACOS) exists as a recognized clinical entity, though its precise definition and diagnostic criteria continue to evolve. ACOS describes patients who exhibit clinical features of both asthma and Chronic Obstructive Pulmonary Disease (COPD) simultaneously. These patients typically present with more severe respiratory symptoms, more frequent exacerbations, poorer quality of life, and more rapid decline in lung function compared to those with either condition alone. Management of ACOS generally involves a combination approach, often including inhaled corticosteroids (such as fluticasone, budesonide, or beclomethasone) combined with long-acting bronchodilators (like salmeterol, formoterol, tiotropium, or umeclidinium) 1. Unlike treating pure COPD, early introduction of inhaled corticosteroids is usually recommended for ACOS patients due to the inflammatory component. Pulmonary rehabilitation, smoking cessation, and appropriate vaccination are also crucial components of management. The biological basis for ACOS likely involves overlapping inflammatory pathways, with both eosinophilic inflammation (typical in asthma) and neutrophilic inflammation (common in COPD) present, along with structural changes to airways that reflect aspects of both conditions.

Key Features of ACOS

• Presence of both asthma and COPD clinical features simultaneously
• More severe respiratory symptoms and frequent exacerbations
• Poorer quality of life and rapid decline in lung function
• Involves overlapping inflammatory pathways and structural changes to airways

Management of ACOS

• Combination approach with inhaled corticosteroids and long-acting bronchodilators
• Early introduction of inhaled corticosteroids due to inflammatory component
• Pulmonary rehabilitation, smoking cessation, and appropriate vaccination are crucial components of management

Diagnostic Criteria

• Diagnosis based on clinical history, physical examination, radiology, and potentially screening questionnaires 1
• Spirometry recommended for confirmation of diagnosis
• Features of asthma and COPD compared to determine likelihood of ACOS

Future Research Directions

• Novel approaches to identify and manage components of heterogeneity in obstructive airway diseases 1
• Personalized treatment approaches based on multidimensional assessment and treatment
• Further research needed to test these novel approaches and improve management of ACOS.

From the Research

Definition and Recognition of ACOS

• Asthma-COPD Overlap Syndrome (ACOS) is a disease phenotype that shares characteristics of both asthma and chronic obstructive pulmonary disease (COPD) 2.
• ACOS is recognized as a clinical entity with persistent airflow limitation and features of both asthma and COPD 3, 4.
• The syndrome is characterized by reversible but persistent airflow limitation, with some features of both asthma and COPD 3.

Clinical Features and Prevalence

• ACOS affects about a quarter of patients with COPD and almost a third of patients who previously had asthma 4.
• Patients with ACOS have significantly worse respiratory symptoms, poorer quality of life, and increased risk of exacerbations and hospital admissions compared to those with asthma or COPD alone 4.
• The prevalence of ACOS has been reported to be between 11-55% in different case series, increasing with age and more frequent in females 3.

Therapeutic Approaches

• Current recommendations for pharmacologic treatment of ACOS are based on a combination of optimal COPD and asthma treatment 3.
• Therapeutic approaches may involve the use of inhalers, phosphodiesterase inhibitors, macrolides, N-acetylcysteine, and statin therapy, depending on patient characteristics and biomarkers 2.
• Future therapeutic approaches should be based on endotypes, with clinical phenotype and underlying endotype-driven clinical studies guiding ACOS guidelines 3.

Controversy and Clinical Utility

• The concept of ACOS is controversial, with some arguing that it is a clinically irrelevant term due to the lack of an accurate diagnosis and inconsistent data regarding prevalence, prognosis, and therapeutics 5.
• Others suggest that recognizing ACOS can guide practical treatment decisions and improve patient outcomes, despite the complexity and heterogeneity of the syndrome 6, 4.