Asthma-COPD Overlap: Challenges to Overcome

Asthma and chronic obstructive pulmonary disease (COPD) are conditions that tend to coexist in individuals, forming the so-called asthma-COPD overlap (ACO). However, defining and understanding ACO comes with its challenges due to various characteristics of patients, criteria, and treatment approaches. In the following, we will be exploring and discussing the complexities of ACO and have a glance at the suggested treatment methods to overcome these challenges.

While identifying ACO, one considers factors like age, chronic airflow limitation, asthma diagnosis, and bronchodilator test results. Based on the mentioned criteria, the estimated prevalence of ACO (within the studied populations) varies widely, ranging from 0.5% to 15%. This kind of discrepancies occur due to differences in study populations, bronchial obstruction severity, and the diverse therapeutic approaches applied. But mainly, the fact that there is no universally applicable definition contributes to the difficulty in accurately assessing ACO's clinical and prognostic implications.

However, there are some approaches used for the diagnosis of ACO that were found to be practical and effective, like the ones proposed by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) and the Spanish Respiratory Society (SEPAR). The SEPAR algorithm is based on age, chronic airflow limitation, asthma diagnosis, and positive bronchodilator tests or eosinophilia (the presence of too many eosinophils in the body). While offering a practical solution for identifying potential ACO cases, the algorithm has a major drawback that lies in grouping patients with distinct characteristics under the ACO umbrella, highlighting the heterogeneity. This is why researchers suggest a strategy to define both specific and measurable objectives for each and every patient.

Due to the heterogeneity of ACO, there exists a need for categorization into distinct phenotypes: eosinophilic COPD and smoking asthmatics. Taking the different pathogenic mechanisms and treatment responses observed in asthma and COPD into account, it becomes essential to tailor treatment approaches for each phenotype.

That brings us to the new way of treatment that is being proposed, which is more suitable to the heterogeneous nature of ACO: It is advocating personalized medicine and emphasizing the need to define patients based on distinct biological, clinical, and social features.

The strategy discourages using a specific type of medication, LABA, only for asthma symptoms and instead recommends combining it with inhaled corticosteroids. If severe symptoms persist, a long-acting antimuscarinic agent (LAMA), may be added. For ongoing symptoms without severe episodes, identifying and treating comorbidities is essential. In some cases, azithromycin might be considered. For those with a specific type of inflammation, monoclonal antibodies are an option. If there's a conditioninvolving widened airways (bronchiectasis) and chronic infections, inhaled antibiotics may be explored. Roflumilast, another medication, is being considered but more evidence is needed to confirm its effectiveness in treating ACO.

To conclude, ACO, which is characterized by the coexistence of asthma and COPD, lacks a universally applicable definition and precise diagnostic criteria. Although there are practical ways to diagnose ACO, the heterogeneity of ACO due to its nature makes it absolutely necessary to form individualized treatment strategies, emphasizing specific and measurable therapeutic objectives for each patient. Of course, further research is crucial to clarify ACO's molecular pathways, identify specific biomarkers, and optimize therapeutic interventions for this complex entity.

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