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The challenge of defining exacerbation in bronchiectasis

One of the most difficult aspects of the study of chronic respiratory diseases is the concept of exacerbation. Defining the limits of each patient's normal daily variations in symptoms, and the minimum time beyond these limits that can be considered the start of an acute process of the disease, poses a challenge that is often insuperable. It is also just as difficult to establish the specific parameters that must be used to define an exacerbation; parameters that are usually grouped as symptoms and/or factors involving the use of health resources or a need for treatment. Nevertheless, in the case of bronchiectasis, and other respiratory diseases, exacerbations (particularly severe exacerbations) have a demonstrable negative impact on a patient's prognosis [1–4] and entail great expense [5, 6], and so their identification, and therefore their definition, is crucial to any early detection and treatment. Ideally, such a definition should present a perfect diagnostic value and, as regards bronchiectasis, be based on reproducible objective measurements linked to inflammation/bronchial infection (biomarkers) and their consequences (acute clinical symptoms). At the moment, however, this approach is not viable for various reasons: we do not have any available biomarkers with sufficient diagnostic value, although there have been some promising studies in this respect [7]; we do not have any sufficiently specific objective measurements for the key symptoms in exacerbations; and, finally, we need to know a patient's previous inflammatory/infectious state in order to quantify the change caused by the supposed exacerbation. Furthermore, there is a significant problem here as a review of the literature reveals a wide range of definitions of bronchiectasis, depending on the studies analysed and the mixture of objective and subjective criteria, making it impossible to compare their results. A worldwide consensus has been reached in the definition of exacerbation in bronchiectasis for research purposes http://ow.ly/SD2P30bFBjX