Difference Between Asthma-COPD Overlap and COPD with Asthma Features
Asthma-COPD Overlap (ACO) is a distinct clinical entity characterized by persistent airflow limitation with features of both asthma and COPD, while COPD with asthma features represents a COPD phenotype that exhibits some asthmatic characteristics but doesn't meet the full diagnostic criteria for ACO. 1, 2
Diagnostic Criteria and Definition
Asthma-COPD Overlap (ACO):
- Requires meeting specific diagnostic criteria according to multiple guidelines:
- GINA/GOLD: Similar number of features from both asthma and COPD
- Spanish guidelines: Two major criteria (FEV₁ increase ≥15% and ≥400 mL, sputum eosinophilia, history of asthma) or one major plus two minor criteria (elevated IgE, atopy history, bronchodilator response ≥12% and ≥200 mL) 1
- Czech guidelines: Two major criteria or one major plus two minor criteria 1
COPD with Asthma Features:
- Primary diagnosis remains COPD
- Shows some asthmatic characteristics (e.g., bronchodilator reversibility, eosinophilia) but insufficient to meet ACO criteria
- Typically has fewer asthmatic features than ACO 2
Key Distinguishing Characteristics
| Feature | Asthma-COPD Overlap | COPD with Asthma Features |
|---|---|---|
| Age | Typically older (mean 64.6 years) | Generally older COPD patients |
| Airflow limitation | Persistent but with significant reversibility | Predominantly fixed with some reversibility |
| Bronchodilator response | Very positive (≥15% and ≥400 mL) | Mild to moderate reversibility |
| Eosinophilia | Often present (≥300 eosinophils/μL) | May be present but not required |
| History | Often includes childhood/previous asthma | Primary smoking history with some asthmatic features |
| Inflammatory pattern | Mixed (eosinophilic, neutrophilic, or both) | Predominantly neutrophilic with some eosinophilic component |
Clinical Implications
Disease Burden
ACO patients experience greater morbidity than either condition alone, with:
- More frequent and severe exacerbations
- Increased hospitalizations
- Worse quality of life
- Possibly increased mortality (HR 1.45,95% CI 1.06-1.98) 2
Treatment Approach
- ACO: Requires combination therapy typically starting with ICS plus LABA, with potential addition of LAMA as disease severity increases 1
- COPD with asthma features: May benefit from ICS addition to bronchodilator therapy, but treatment remains primarily COPD-focused 3
Diagnostic Algorithm
- Confirm chronic airflow limitation in a smoker/ex-smoker ≥35 years old
- Assess for:
- Current diagnosis of asthma OR
- Very positive bronchodilator test (≥15% and ≥400 mL) OR
- Blood eosinophilia (≥300 eosinophils/μL)
- If #1 plus any criteria in #2 are present → ACO diagnosis
- If #1 is present with some but insufficient criteria from #2 → COPD with asthma features 3
Common Pitfalls in Diagnosis
- Relying solely on bronchodilator reversibility: BDR alone has been found to be non-reproducible and not specific for ACO diagnosis 1
- Overlooking inflammatory markers: Blood eosinophil counts and other biomarkers are crucial for proper classification
- Age-based assumptions: While ACO is more common in older patients, it can develop from childhood asthma that progresses to fixed airflow limitation 1
Clinical Pearls
- Severe childhood asthma significantly increases the risk of developing ACO in adulthood 1
- Approximately 20% of patients with obstructive airway diseases have features of ACO 2
- ACO patients are typically excluded from clinical trials, limiting the evidence base for treatment decisions 2
- The systemic inflammatory profile in ACO more closely resembles COPD than asthma 2
Understanding these distinctions is crucial for appropriate management decisions that can significantly impact morbidity, mortality, and quality of life in these patients.