Nasal airway ion transport is linked to the cystic fibrosis phenotype in adult patients.

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 <50% of predicted value) were more likely to have an enhanced response to amiloride solution (OR 3.7 (95% CI 1.3 to 11.0), p = 0.02). However, there was no significant relationship between nasal potential difference and the severity of the genotype. CONCLUSIONS Nasal epithelial ion transport in cystic fibrosis is linked to the clinical expression of the disease. The pancreatic status appears to be mostly related to the defect in epithelial chloride secretion whereas the respiratory status is mostly related to abnormal sodium transport and the regulatory function of the CFTR protein.