Asthma or COPD? Identifying overlapping features and choosing the right therapy

Which clinical features or patterns in a patient’s history should prompt you to consider asthma–COPD overlap rather than asthma or COPD alone?

Firstly, the terminology has evolved: asthma–COPD overlap is no longer commonly used, as both GINA and GOLD have moved away from the term in recent guidelines. At present, we do not have a single label for patients who have some features of asthma and some features of COPD.

However, from a clinical treatment perspective, this remains very important. When you first see a patient—for example, someone aged 55 with obstructive lung disease—it is the job of the respiratory physician to determine whether the presentation is more asthma-dominant or more COPD-dominant, because the treatment options are quite different. Sometimes this is difficult, but we still need to identify which disease is predominant in that patient.

How should lung function tests be used when assessing possible ACO, and what are the key limitations of spirometry and bronchodilator response in distinguishing overlap?

When I was at medical school, things seemed simple. A patient had lung function testing, received a bronchodilator, and if they showed reversibility, we called it asthma. If they did not, we called it COPD.

Today, we know it is more complex than that. At least half of patients with COPD can respond to a short-acting beta agonist, so lung function alone is not enough. A very important additional measurement is diffusion capacity. COPD leads to destruction of lung tissue, so diffusion capacity is often reduced.

If patients have abnormal lung function but normal spirometry, that points more towards asthma. If spirometry is abnormal and diffusion capacity is also reduced, that suggests COPD. From a lung function perspective, that can be very helpful in distinguishing the dominant disease.

What role do biomarkers and additional investigations play in supporting or refuting the diagnosis of ACO in everyday practice?

That is a very important question, because this is something we still fail to implement consistently. When making a diagnosis of asthma or COPD, biomarkers should be measured early, because later in the patient’s journey we need those results to guide phenotype-based therapy.

The clear recommendation is to measure eosinophils, FeNO, and IgE, because we now have therapies linked to these markers. This is something we should encourage colleagues to do whenever they first diagnose obstructive lung disease, so that treatment can be tailored later in the patient’s course.

How do you approach treatment selection when managing a patient with features of both asthma and COPD, particularly with regard to inhaled corticosteroids and bronchodilator therapy?

One of the most important questions is whether the patient has a history of exacerbations. According to the guidelines, many COPD patients with exacerbations should receive inhaled corticosteroids (ICS). Therefore, if a patient has an exacerbation history, the exact label becomes less important because ICS is already indicated. If eosinophil levels are high, that is an even stronger signal that a patient with COPD may benefit from ICS.

In our clinic, we also perform a lot of CT imaging of the lungs. A CT scan can help show whether the pattern is more chronic bronchitic, more emphysematous, or more suggestive of asthma. Today, we have tools such as biomarkers, imaging, and radiomics that help us distinguish these conditions more accurately.

The challenge is that this is easier in specialist centres with ready access to imaging. Globally, it may be more difficult to obtain high-quality CT scans or have someone experienced enough to interpret them properly. That is why I believe artificial intelligence will help in the near future—using imaging to identify whether the patient has COPD, asthma, mixed features, and which factor is predominant.

What are the most common pitfalls that lead to misclassification of ACO, and how can clinicians avoid these to ensure appropriate therapy?

The key issue is access to the right therapies. We now have many new treatments for severe asthma, including biologics. If a patient is misclassified as having COPD, they may never gain access to those options.

If, instead, the patient is recognized as being more on the asthma side, for example, with eosinophilia, elevated FeNO, or other signals, then we have a much broader range of therapies available.

The treatment goals are also different. In asthma, I want to aim for remission on treatment if possible. In COPD, there is often ongoing progression, so the goal may be to stabilize the disease. That means the conversation with the patient is completely different depending on whether you frame them as a severe asthma patient with persistent nerve obstruction, or a COPD patient with obstruction and a smoking history.

How can response to initial therapy help confirm or review ACO and guide ongoing management?

The key point is this: if a clinician is unsure whether the patient is more COPD or more asthma, they still need to make their best initial judgement, start treatment according to the relevant guidelines, and review the patient again after around 3 months.

If the patient is not responding well or continues to have significant problems, then the original diagnosis should be reconsidered. The clinician may need to shift the diagnosis more towards asthma or more towards COPD, which in turn changes both the treatment plan and the therapeutic goals.

We do not know everything, and the initial diagnosis may be wrong. What matters is reassessing after treatment and being willing to revise the diagnosis if needed.