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Dear editor
We have read with great interest the letter by Kolsum et al. [1] and we fully agree that eosinophilic COPD (e-COPD) patients have distinct characteristics compared to smoking asthmatics (SA) who develop non-fully reversible airflow obstruction. Both entities are commonly encompassed under an umbrella term [2], the so-called Asthma-COPD overlap (ACO), but, in the age of personalized medicine [3], it might be unacceptable to offer the same treatment for two related but different conditions. Studies that focus on identifying ACO’s phenotypes are scarce, but Lange et al. found that individuals with ACO and asthma onset before the age of 40 years have better prognosis than those whose asthma starts after this age [4]. On the other hand, given that asthma and COPD are themselves heterogeneous diseases, one could argue whether it is necessary to define their overlap as a new entity. All these problems could be sorted out by identifying endotypes of obstructive lung disease (OLD) that would allow a personalized approach to therapy. In this regard, we have recently published a study that postulated the extinction of ACO and the use of a Th2 inflammation biomarker to differentiate a pooled population of patients with OLD [5]. With this letter, we would like to provide additional information to support the differentiation between e-COPD and SA.
We have performed a cross-sectional, observational, multicenter study carried out in 23 out-patient clinics from tertiary hospitals in Spain. The details of the design are described elsewhere [5]. Two hundred and ninety-two patients with OLD were included in the study: 94 non-smoking asthmatics, 89 non-eosinophilic COPD, 44 SA and 65 e-COPD. All investigators were asked to prospectively recruit 12 consecutive eligible patients with OLD from their clinics.
Patients were labelled as SA if they had been previously diagnosed with asthma according to GINA guidelines [6] and, after having smoked >20 pack-years, they subsequently developed non-fully reversible airflow obstruction (FEV1/FVC <70% post-bronchodilator). The diagnosis of e-COPD was made in patients who were previously diagnosed with COPD according to GOLD recommendations [7], in the absence of a clinical suspicion for asthma and in the presence of a blood eosinophil count >200 eosinophils/?l.
There were important differences between patients with SA and e-COPD (Table 1). Patients classified as e-COPD were older...