The Importance of Phenotyping Bronchiectasis

between idiopathic bronchiectasis (i.e. unidentified aetiology after complete diagnostic workup) and ‘undetermined’ bronchiectasis (i.e. unidentified aetiology with incomplete diagnostic workup) seems more stringent and appropriate than in other publications from the past. Secondly, the proposed groups are related to the underlying aetiology of bronchiectasis, are easily identifiable and provide useful information for clinical management. Indeed, the authors identify nine aetiology groups: idiopathic, post-infectious, COPD-related, asthma-related, congenital, immunodeficiency, auto-immune, tumour and other. Among these, the COPD-related group clearly showed differential characteristics: an imbalance in gender ratio (male/female = 2.2), the highest prevalence of smokers (as expected), the highest median age at diagnosis, a higher prevalence of Pseudomonas aeruginosa and the worst lung function at diagnosis. On the other hand, idiopathic bronchiectasis showed the highest prevalence of females (male/female = 0.23) and the most preserved lung function at diagnosis. Finally, post-infectious bronchiectasis did not show distinguishable characteristics. Numerous studies have investigated the combination of COPD and bronchiectasis, showing different prevalence rates (from 2 to 50%) depending on cohort and primary diagnosis considered (COPD or bronchiectasis) [1, Bronchiectasis is considered to be one of the most heterogeneous respiratory diseases due to both multiple etiological conditions and variable clinical manifestations. This huge heterogeneity is one of the main reasons for disease complexity, and thus, there is a need to identify clinical phenotypes which have specific therapeutic and follow-up indications as in other respiratory diseases [i.e. chronic obstructive pulmonary disease (COPD) or asthma]. Unfortunately, identifying phenotypes of bronchiectasis is not an easy task, and so far, attempts to link aetiology to clinical severity have failed [1] . Aliberti et al. [2] performed an interesting cluster analysis that identified four phenotypes based on microbiological and clinical features (‘ Pseudomonas ’, ‘other chronic infection’, ‘daily sputum’ and ‘dry bronchiectasis’) but not on the different aetiologies of the disease. These phenotypes clearly showed different outcomes (quality of life, exacerbations, hospitalisations and mortality) and highlighted the importance of a more personalised approach to bronchiectasis. More recently, Buscot et al. [3] presented a retrospective study aimed at describing the clinical, functional and microbiological phenotypes according to different aetiologies of bronchiectasis. This study has several strengths. First of all, the proposed diagnostic flowchart reduced the group classified as idiopathic to 11%. The distinction Published online: September 3, 2016