Lung clearance index to detect the efficacy of Aztreonam lysine inhalation in patients with cystic fibrosis and near normal spirometry – A single-centre feasibility study

Comparing the efficacy of inhaled antibiotics can be difficult in small groups of patients with cystic fibrosis and mild lung disease. In a feasibility study we compared Aztreonam lysine for inhalation solution (AZLI; Cayston®) to standard inhaled antibiotic therapy in patients with cystic fibrosis and near normal spirometry. To detect treatment responses we used both lung clearance index (LCI) and forced expiratory volume in one second (FEV1). At baseline, median FEV1 was 87% pred. and median LCI was 8.6 (upper limit of normal: 7.0). After 4 weeks, LCI improved by -0.36 after AZLI and deteriorated by +0.12 after tobramycin treatment (p = 0.039). No significant differences between treatments (p = 0.195) were observed using FEV1. These results suggest that lung clearance index can be used to detect treatment induced changes in subjects with mild lung disease.