Endobronchial optical coherence tomography or computed tomography for evaluating progression of bronchiectasis

Background The early radiological signs of progression in bronchiectasis remain unclear. The objective of the present study was to compare endobronchial optical coherence tomography (EB-OCT) and chest computed tomography (CT) for the evaluation of radiological progression of bronchiectasis via stratification of the presence (TW+) or absence (TW-) of thickened-walled bronchioles surrounding dilated bronchi in patients with bronchiectasis based on CT, and determine the risk factors. Methods In this prospective cohort study, we performed both chest CT and EB-OCT at baseline and 5-year follow-up, to compare changes in airway calibre metrics. We evaluated bacterial microbiology, sputum matrix metalloproteinase-9 levels and free neutrophil elastase activity at baseline. We compared clinical characteristics and airway calibre metrics between the TW+ and TW- groups. We ascertained radiological progression at 5 years via CT and EB-OCT. Results We recruited 75 patients between 2014 and 2017. At baseline, EB-OCT metrics (mean luminal diameter (p=0.017), inner airway area ( p=0.005) and airway wall area ( p=0.009) of seventh-to ninthgeneration bronchioles) were significantly greater in the TW+ group than in the TW- group. Meanwhile, EB-OCT did not reveal bronchiole dilatation (compared with the same segment of normal bronchioles) surrounding nondilated bronchi on CT in the TW- group. At 5 years, 53.1% of patients in the TW+ group progressed to have bronchiectasis measured with EB-OCT, compared with only 3.3% in TW- group ( p<0.05). 34 patients in the TW+ group demonstrated marked dilatation of medium-sized and small airways. Higher baseline neutrophil elastase activity and TW+ bronchioles on CT predicted progression of bronchiectasis. Conclusion Thickened-walled bronchioles surrounding the dilated bronchi, identified with EB-OCT, indicates progression of bronchiectasis.