Asthma and COPD are common diseases which can co-occur, and this is not a new concept. The resurgence in interest has likely arisen due to our desire to phenotype individuals better, to personalise treatments and because of our shift in thinking about when to use inhaled corticosteroids in people with COPD. There are biologic as well as clinical similarities to asthma and COPD which can make differentiation between them complex.
What’s the definition of asthma and COPD overlap?
There’s no consensus definition or gold standard test for making a diagnosis of asthma and COPD overlap.1 To truly have overlap, a patient should have persistent airflow limitation in addition to several features usually more common in asthma and some usually more commonly found in people with COPD.
In practice, this means undertaking spirometry and taking a good clinical history to understand what symptoms are present. Radiology may also be helpful (presence of emphysema in someone with significant FEV1 reversibility for example). Some definitions even suggest the presence of eosinophilia in a current smoker with airflow obstruction is enough.
Another way of thinking about it would be to consider it in individuals who have a diagnosis of asthma or COPD but their disease burden is above and beyond that of one disease alone. A typical patient may be over 40 years of age, had a diagnosis of asthma much earlier on in life that was treated/is still on treatment, in addition to a significant smoking history and obstruction on spirometry.
Getting the diagnosis right might not be straightforward and may even require referring a patient to secondary care for extra investigations.
The most important thing when treating COPD or asthma alone or overlap, is ensuring the diagnosis is right before commencing treatment.
How common is it?
It’s important to remember that most people with asthma will not go on to develop COPD and vice versa. Having both diseases is much less common than one disease on its own. Studies have suggested a prevalence of overlap of between 1.6% and 4.5% in the general population depending on age, increasing to 32% in people with asthma or COPD depending upon the definition used. In reality, it is likely closer to 15% in this population.2-4 Misdiagnosis, and disease misclassification are common.
How do I treat asthma and COPD overlap?
The first step in management is getting the diagnosis right.
Initial treatment should focus on the asthma component first, so using inhaled corticosteroids (ICS); low or moderate dose, depending upon symptoms.5 One of the aims here being to improve quality of life.
Long acting beta agonists and long acting muscarinic antagonists can then be added in as needed, followed by additional asthma and COPD management strategies depending upon the dominant disease contributing to symptom burden at the time.
It’s important to note that this strategy hasn’t formally been studied, however, given the importance of ICS treatment in people with asthma and the guidance to avoid ICS in COPD where not indicated, this seems a reasonable approach. It also highlights why initial correct diagnosis is so important.6
Improvement or reduction of modifiable risk factors as appropriate is also essential. This could mean encouraging patients to improve their physical activity, undertake pulmonary rehabilitation, smoking cessation, allergen avoidance and treatment of co-morbidities.
Why is it important to recognise?
People with asthma COPD overlap are thought to have a greater symptom burden, worse quality of life, higher exacerbation risk and so greater healthcare utilisation and healthcare costs.7 How overlap of both diseases contributes to longer term outcomes however is not known.
There is a lot about asthma COPD overlap we just don’t know yet. Even amongst experts there is considerable variability in defining diagnosis. There remains no consensus on definition, or what constitutes optimal management. Studies are needed to fill this evidence gap. There has been a move away from considering this to be a syndrome and the term asthma and COPD overlap is now encouraged instead. As guidelines have updated there has been a shift in definitions and in this day in age its not as straightforward as a tick box exercise as suggested by older guidelines.
Asthma and COPD are common diseases which can co-occur but what also happens, is that people are incorrectly diagnosed with one or the other and end up with both disease labels in their medical records.
Getting the diagnosis right and even taking away incorrect diagnostic labels is important as it helps to manage patient expectations and as healthcare professionals gives us an idea as to what we are trying to achieve with treatment in addition to making sure our patient is receiving the right treatment.
Sometimes it is not all that easy to differentiate between the two, in particular in people who are older and who smoke. This is not to say that everyone who smokes automatically has COPD or that people with asthma never smoke.
de Marco, Roberto et al. The coexistence of asthma and chronic obstructive pulmonary disease (COPD): prevalence and risk factors in young, middle-aged and elderly people from the general population. PloS one vol. 8,5 e62985. 10 May. 2013. https://doi.org/10.1371/journal.pone.0062985
Nissen F, Morales DR, Mullerova H, Smeeth L, Douglas IJ, Quint JK. Concomitant diagnosis of asthma and COPD: a quantitative study in UK primary care. Br J Gen Pract. 2018 Nov;68(676):e775-e782. https://doi.org/10.3399/bjgp18X699389
D.J. Maselli, M. Hardin, S.A. Christenson, N.A. Hanania, C.P. Hersh, S.G. Adams, A. Anzueto, J.I. Peters, M.K. Han, F.J. Martinez, Clinical Approach to the Therapy of Asthma-COPD Overlap, Chest, Vol 155, Issue 1, 2019, Pages 168-177. https://doi.org/10.1016/j.chest.2018.07.028
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