The effect of N-acetylcysteine in patients with non-cystic fibrosis bronchiectasis (NINCFB): study protocol for a multicentre, double-blind, randomised, placebo-controlled trial

Background: N-acetylcysteine (NAC), which is specifically involved in airway mucus clearance and antioxidation, is recommended by the treatment guideline for non-cystic fibrosis bronchiectasis (NCFB). However, there is little clinical evidence of its long-term efficacy concerning quality of life (QoL) and exacerbation in patients with NCFB. In addition, the influences of NAC on airway bacterial colonization, chronic inflammation and oxidative stress in NCFB are also unclear. Methods: NINCFB is a prospective, multicentre, double-blind, randomised, placebo-controlled trial that will recruit 119 patients with NCFB and randomly divide them into an NAC group (n = 79) and a control group (n = 40). Participants in the NAC group will receive 600 mg oral NAC twice daily for 52 weeks, while patients in the control group will receive 600 mg placebo twice daily for 52 weeks. The information at baseline will be collected once participants are enrolled. The primary endpoints are the changes in St George's Respiratory Questionnaire scores and the number of exacerbations in 52 weeks. The secondary endpoints are the 16S rRNA of sputum and the levels of inflammatory factors and oxidative stressors in sputum and serum. Other data related to radiography, lung function tests, number of oral and/or intravenous antibiotic therapies and adverse events (AEs) will also be analysed. Further subgroup analysis distinguished by the severity of disease, severity of lung function, airway bacterial colonization and exacerbation frequency will be performed. Discussion: The objective of this study is to determine the long-term efficacy of NAC on QoL and exacerbation of NCFB and to explore the effectiveness of NAC for antibiosis, anti-inflammation and antioxidation in NCFB. The study results will provide high-quality clinical proof for the revision and optimization of treatment guidelines and for expert consensus on NCFB treatment.