Asthma COPD Overlap Syndrome ICD-10: Diagnosis and Coding

Asthma-COPD Overlap Syndrome (ACOS) presents a diagnostic and coding challenge due to its overlapping features of asthma and chronic obstructive pulmonary disease (COPD). Proper identification ensures accurate treatment, reimbursement, and epidemiological tracking. Clinicians and medical coders must distinguish ACOS from standalone asthma or COPD while adhering to ICD-10 classification guidelines.

Pathophysiological Intersection

Asthma-COPD Overlap Syndrome (ACOS) involves airway inflammation, structural remodeling, and airflow limitation, combining characteristics of both asthma and COPD. Asthma is driven by eosinophilic inflammation and reversible bronchoconstriction, while COPD features neutrophilic inflammation, progressive airflow obstruction, and alveolar destruction. ACOS exists at this intersection, complicating diagnosis and management.

A key feature of ACOS is the coexistence of airway hyperresponsiveness and persistent airflow limitation. Spirometry often reveals a partially reversible response to bronchodilators, distinguishing ACOS from asthma, which typically shows complete reversibility. This persistent obstruction results from chronic inflammation, airway remodeling, and small airway fibrosis, more characteristic of COPD. However, ACOS patients retain some bronchodilator responsiveness, reflecting the asthmatic component.

Inflammatory profiles highlight this overlap. Asthma is associated with type 2 inflammation, marked by elevated eosinophils and interleukin (IL)-4, IL-5, and IL-13 activity, while COPD is driven by neutrophilic inflammation and cytokines like tumor necrosis factor-alpha (TNF-α) and IL-8. ACOS patients often exhibit a mixed inflammatory pattern, leading to increased exacerbations, greater symptom burden, and a more rapid decline in lung function.

Structural changes further reflect ACOS’s hybrid nature. Asthma-related airway remodeling includes subepithelial fibrosis, goblet cell hyperplasia, and increased smooth muscle mass, contributing to narrowing and hyperreactivity. COPD remodeling involves small airway obliteration, loss of elastic recoil, and emphysematous destruction. ACOS patients display both airway wall thickening and emphysematous changes, complicating differentiation.

Clinical Presentation

Patients with ACOS present with symptoms reflecting both asthma and COPD. Dyspnea is persistent yet fluctuates more than in COPD alone. Patients report episodic breathlessness triggered by allergens, cold air, or exercise—suggestive of asthma—alongside exertional dyspnea that worsens over time, resembling COPD.

Cough characteristics vary. Many ACOS patients experience chronic cough with sputum production, typical of COPD, yet may also have nocturnal or early morning coughing spells, more common in asthma. Wheezing is persistent but fluctuates in intensity, reflecting airway hyperreactivity and fixed obstruction. Chest tightness worsens at night or upon waking, a pattern reminiscent of asthma, but discomfort may persist despite bronchodilator use, akin to COPD.

Exacerbations occur more frequently and severely in ACOS compared to asthma or COPD alone. Triggers include respiratory infections, environmental pollutants, and allergens, leading to sudden symptom worsening that may require hospitalization. Unlike COPD exacerbations, primarily infection-driven, ACOS exacerbations often involve an inflammatory component responsive to corticosteroids, though not as effectively as in asthma. Recovery is prolonged, increasing the risk of subsequent flare-ups and contributing to rapid lung function decline.

ICD-10 Coding Approach

ACOS does not have a distinct ICD-10 code, requiring separate codes for asthma and COPD based on clinical features. Accurate documentation ensures appropriate reimbursement, epidemiological tracking, and treatment decisions.

Asthma Codes

Asthma falls under ICD-10 category J45, with subcategories based on severity and control. Mild, moderate, and severe persistent asthma are coded as J45.30, J45.40, and J45.50, respectively, while intermittent asthma is assigned J45.20. Acute exacerbations include a fifth character, such as J45.21 for intermittent asthma with exacerbation. Status asthmaticus is designated by J45.22. Documentation should specify whether asthma is allergic (J45.0), nonallergic (J45.1), or mixed (J45.8), as this distinction influences treatment. Eosinophilic asthma, increasingly recognized in ACOS, is coded under J82.83.

COPD Codes

COPD is classified under ICD-10 category J44. The general code for unspecified COPD is J44.9, while COPD with acute exacerbation is J44.1. Chronic bronchitis is coded J44.0, and emphysema under J43.9. Given ACOS’s overlap, careful documentation is needed. Tobacco dependence or history should be coded from category F17.2 or Z87.891.

Combined Assignment

Since ACOS lacks a unique ICD-10 designation, both asthma and COPD codes must be assigned. A typical combination includes J44.9 for COPD and J45.50 for severe persistent asthma, with additional modifiers for exacerbations if applicable. Sequencing depends on the primary reason for the encounter. If hospitalization is due to an asthma exacerbation, the asthma code is listed first, followed by the COPD code. For a COPD-related exacerbation, J44.1 takes precedence. Including relevant comorbidities, such as respiratory failure (J96.0) or chronic respiratory infections (J98.8), provides a comprehensive clinical picture.

Associated Comorbidities

ACOS patients have a higher burden of comorbid conditions. Cardiovascular diseases, including hypertension and ischemic heart disease, are common. Chronic systemic inflammation contributes to endothelial dysfunction and arterial stiffness, increasing the risk of myocardial infarction and stroke. A Lancet Respiratory Medicine study found ACOS patients had a 1.6-fold higher likelihood of heart failure compared to those with COPD alone.

Metabolic disorders, including diabetes and obesity, are also prevalent. Frequent systemic corticosteroid use contributes to insulin resistance and weight gain. A Chest study reported nearly 40% of ACOS patients exhibited metabolic syndrome, characterized by central obesity, dyslipidemia, and impaired glucose tolerance. These metabolic disturbances exacerbate respiratory symptoms by increasing systemic inflammation and reducing lung compliance.

Psychiatric conditions such as depression and anxiety are another major concern. Persistent breathlessness and frequent exacerbations contribute to psychological distress. A Thorax meta-analysis found ACOS patients were twice as likely to suffer from depression compared to those with COPD alone. Sleep disturbances, particularly obstructive sleep apnea (OSA), further compound these challenges, worsening nocturnal hypoxemia and exacerbation frequency. Careful screening and management are essential.