Transepithelial nasal potential difference (NPD) measurements in cystic fibrosis (CF).

The main underlying physiologic abnormality in cystic fibrosis (CF) is dysfunction of the CF transmembrane conductance regulator (CFTR), which results in abnormal transport of sodium and chloride across epithelial surfaces. CFTR function could be tested in vivo using measurements of nasal transepithelial potential difference (PD). Nasal measurements show characteristic features of CF epithelia, including hyperpolarized baseline readings (basal PD), excessive depolarization in response to sodium channel inhibitors, such as amiloride (ΔAmiloride), and little or no chloride (Cl-) secretion in response to isoproterenol in a chloride-free solution (ΔCl- free-isoproterenol). PD test is applied for CF diagnosis and monitoring of new therapeutic modulations and corrections.