Etiology and characteristics of patients with bronchiectasis in Taiwan: a cohort study from 2002 to 2016

Background Bronchiectasis is a chronic infectious respiratory disease with diverse causes and ethnic or geographic differences. However, few large-scale studies of its etiology have been conducted in Asia. This study aimed to determine the etiology and clinical features of bronchiectasis in Taiwan. Methods This longitudinal cohort study investigated the etiology and clinical features of newly diagnosed non-cystic fibrosis bronchiectasis patients from January 2002 to December 2016. The clinical, functional and microbiological data of patients were retrieved from the Chang Gung Research Database, which includes seven medical facilities throughout Taiwan. The index date was the date of the first bronchiectasis diagnosis. Known diseases that were diagnosed before the index date were regarded as etiologies of bronchiectasis. Results The cohort comprised 15,729 adult patients with bronchiectasis. Idiopathic (32%) was the most common cause, followed by post-pneumonia (24%). Other causes included post-tuberculosis (12%), chronic obstructive pulmonary disease (14%), asthma (10%), gastroesophageal reflux disease (2%) and rheumatic diseases (2%). At diagnosis, 8487 patients had sputum culture. Pseudomonas aeruginosa (5.3%) was the most common bacteria, followed by non-tuberculosis mycobacteria (3.6%), Haemophilus influenzae (3.4%) and Klebsiella pneumoniae (3.1%), but 6155 (72.1%) had negative sputum cultures. Patients with post-tuberculosis had a higher sputum isolation rate of non-tuberculosis mycobacteria than P. aeruginosa. Patients with post-tuberculosis and post-pneumonia bronchiectasis had a higher frequency of chronic lung infection than other groups (p < 0.05). Clinical characteristics, such as gender, lung function, comorbidities and microbiology, were significantly different between idiopathic and known etiologies. Conclusions Idiopathic, post-infection and tuberculosis constitute major bronchiectasis etiologies in Taiwan. Clinical characteristics and sputum microbiology were distinct among separate etiology phenotypes.