Disclaimer:
Asthma-COPD overlap is NOT a formally recognised / described diagnosis by UK guidelines. This article is based on the GINA guidelines, as asthma-COPD overlap is included in the UKMLA content map as a separate condition to asthma and COPD.
Asthma and COPD are covered in separate articles
Definition
Asthma-COPD overlap is a term used to describe patients who have persistent airflow limitation with clinical features of both asthma and COPD.
It is not a single disease entity but describes a heterogeneous group of patients with various underlying mechanisms.
Clinical Features
If features are not fully explained by asthma or COPD alone, consider asthma-COPD overlap.
| Age of onset | Either is possible:
|
| Triggers | Symptoms are often triggered by factors common in asthma, such as:
|
| Exposure history | There is often a significant history of:
|
| Symptoms | Respiratory symptoms such as dyspnea, cough, chest tightness, and wheeze may be intermittent or episodic rather than constant |
| Other history |
|
Disease Course and Prognosis
Compared to patients with just asthma or just COPD, patients with asthma-COPD overlap have:
- More frequent and severe exacerbations
- Poorer quality of life
- A more rapid decline in lung function over time
- Higher mortality rates
Objective Tests / Diagnostic Criteria
Asthma-COPD overlap is characterised by the presence of BOTH:
- Persistent airflow limitation (a typical COPD feature), and
- Asthma features (e.g. evidence of variable airflow limitation, marked bronchodilator reversibility, raised FeNO or eosinophilia)
Lung Function Tests
| Criteria | Finding / description | Role in diagnosis |
|---|---|---|
| Persistent airflow limitation | Post-bronchodilator FEV1/FVC ratio <0.7 | Mandatory for diagnosis |
| Marked bronchodilator response | FEV1 increase of >12% and 400 mL from baseline | Highly unusual in pure COPD, strongly indicates asathma component |
| Diurnal PEFPeak expiratory flow variability | Average daily diurnal variability >10% in adults | Note that a normal PEF does NOT rule out asthma-COPD overlap |
Specialised Tests
Specialist investigations are not strictly required for every patient if the clinical history and lung function test findings are clear.
Referral for specialised testing is recommended if there is 1) persistent symptoms despite treatment or 2) uncertain diagnosis or 3) atypical symptoms – e.g. significant weight loss, haemoptysis.
Key specialised tests:
| Test | Description / findings |
|---|---|
| DLCODiffusing capacity of the lungs for carbon monoxide | Often reduced in COPD-asthma overlap
Typically normal or slightly elevated in asthma |
| HRCTHigh-resolution CT | Used to identify emphysema / air trapping / increased bronchial wall thickness |
| Biomarkers | The following tests can support / suggest type II airway inflammation characteristic of asthma
|
Management
The core treatment principle is treating the asthma component initially to prevent life-threatening exacerbations.
Key principle:
- ICS-containing therapy is mandatory (e.g. usually budesonide/formoterol)
- Do NOT treat asthma-COPD overlap with long-acting bronchodilator monotherapy
Disclaimer:
As mentioned above, there is no UK guideline on asthma-COPD overlap. The management outlined above is therefore based on GINA guidelines, which recommend treating initially according to the asthma pathway.
In an exam context, it is reasonable to follow the standard UK asthma gudieline, see Asthma (Chronic).