It is not yet known what quantity of change for any of these parameters would be considered clinically significant, but other studies have shown a reduction in airway wall thickness of 3% in response to hypertonic saline in young children (15), a 3% reduction in response to azithromycin in infants with CF (16), and 12% reduction in adults in response to CFTR modulators (17). This evidence concerns the gene CFTR and cystic fibrosis.