Background: This study was conducted to determine whether the major nasal airway ion transport abnormalities in cystic fibrosis (that is, defective cAMP regulated chloride secretion and basal sodium hyperabsorption) are related to the clinical expression of cystic fibrosis and/or to the genotype. Methods: Nasal potential difference was measured in 79 adult patients with cystic fibrosis for whom clinical status, respiratory function, and CFTR genotype were determined. Results: In univariate and multivariate analysis, patients with pancreatic insufficiency were more likely to have low responses to low chloride (odds ratio (OR) 8.6 (95% CI 1.3 to 58.5), p = 0.03) and isoproterenol (OR 11.2 (95% CI 1.3 to 93.9), p = 0.03) solutions. Similarly, in univariate and multivariate analysis, patients with poor respiratory function (forced expiratory volume in 1 second
