LAUSR

RATIONALE In cystic fibrosis, information on the efficacy of azithromycin past 12 months of treatment is still scarce. OBJECTIVE The study sought to quantify the changes in lung function and the number of intravenous antibiotic courses after initiation of azithromycin in patients included in the French Cystic Fibrosis Registry. METHODS The study followed-up 1,065 children and 990 adults from 2 years before to 5 years after long-term azithromycin treatment initiated between 2001 and 2011. Mixed change-point models were used to quantify the changes in the forced expiratory volume in one second and the yearly number of intravenous antibiotic courses. RESULTS In the year of treatment initiation, the mean forced expiratory volume was significantly higher than expected (+1.6%, p=0.007 in children and +1.3%, p=0.02 in adults). The decline of the forced expiratory volume over time was less marked after than before treatment initiation (slope difference: +0.7% per year, p=0.03 in children and +0.6% per year, p=0.06 in adults). The mean increase in the yearly number of intravenous antibiotic courses was lower after than before treatment initiation. The rate ratio quantifying the effect on the mean increase was 0.93 (95% CI: [0.88; 0.99]; p=0.02) in children and 0.95 (95% CI: [0.90; 1.01]; p=0.08) in adults. CONCLUSION In children, long-term azithromycin treatment was associated with immediate and sustained beneficial changes in lung function and sustained beneficial changes in the frequency of pulmonary exacerbations. In adults, it was associated with immediate beneficial changes in lung function.