Asthma and COPD: are they so different?

Chronic obstructive pulmonary disease (COPD) is a disease showing a sharp rise in mortality and morbosity. Often however the mortality due to COPD is underestimated. There thus exists an apparent discordance. Moreover some forms of COPD evolve towards more complex clinical pictures overlapping with other diseases (e.g. bronchial asthma). According to current international guidelines, the diagnosis of COPD requires an FEV(1) and FVC ratio lower than 70%. A limitation of this definition is precisely the fact that it unites morbose forms under a single diagnosis on the basis of the FEV(1)/FVC ratio and does not always permit to distinguish different clinical forms such as COPD and bronchial asthma, or the presence of a systemic involvement and of other comorbidities, that contribute to worsening the clinical picture and the disease prognosis. In the setting of COPD there exist diverse phenotypes and at times there is an evident overlap with bronchial asthma, but it is known that there exist some forms of asthma with non reversible obstruction and vice versa some forms of COPD with partially reversible obstruction. Within COPD there are diverse forms in which the various exogenous risk factors interact with predisposing genetic factors, which necessitate a far more complex diagnostic iter than the simple evaluation of FEV(1). Often however it is difficult to differentiate some forms due to the co-presence of genetic factors (atopy) or environmental factors (cigarette smoke), that contribute to creating clinical pictures that are hard to differentiate and for which the term "asthmatic bronchitis" has been created. Hence if one uses only the parameter of airflow limitation and its reversibility or not, one risks attributing to the diagnosis of asthma the majority of patients with bronchial obstruction. According in fact to a recent epidemiological study following the criterion of the presence of reversibite bronchial obstruction as a diagnostic parameter, approximately 53% of subjects with obstruction belonged to the asthma phenotype. The clinical history and pathogenetic factors, but also the assessment of other markers can certainly help to discern the diverse phenotypes. A better understanding of the relative proportions of each phenotype of COPD and of the existence of "overlapping" syndromes should lead to a redesigning of clinical studies so that they take into account these clinical forms in order to identify subjects affected by COPD with an asthmatiform phenotype that has distinct therapuetic responses and clinical outcomes. At the therapeutic level such pathophysiological evidence implies some treatment difficulties in that the GOLD international guidelines for COPD and GINA for asthma exclude from their treatment recommendations precisely those patients with an overlap of the two diseases or in whom a differential diagnosis is not possible.