Relationships between nasal potential difference and respiratory function in adults with cystic fibrosis

This study investigated the relations between nasal transepithelial electri c potential difference (PD) and the phenotype and genotype of cystic fibros is (CF) adult patients. Basal nasal PD was measured in 95 adult CF patients who were classified int o three groups of nasal PD (expressed as absolute values) according to the 10th and the 90th percentiles (28.3 and 49.2 mV, respectively), which defin ed group 1 (nasal PD less than or equal to 28.3 mV), group 2 (nasal PD 28.3 -49.2 mV) and group 3 (nasal PD greater than or equal to 49.2 mV), Patients from group 1 had a higher forced vital capacity (FVC) than patient s from groups 2 and 3 (76.5+/-22.4 versus 57.4+/-21.2 and 55.7+/-21.1% pred icted, respectively, p<0.05) and a higher forced expiratory volume in one s econd (FEV1) (69.3+/-24.0 versus 42.5+/-22.4 and 42.2+/-21.4% pred, respect ively, p<0.01),Among patients with severe mutations (Delta F508 homozygote, or one Delta F508 mutation plus another "severe" mutation, or two "severe" mutations), patients from group 1 had a higher FVC, FEV1 and arterial oxyg en tension than patients from groups 2 and 3 (p<0.05 for each comparison). The results show that in adult cystic fibrosis patients a normal basal nasa l potential difference is related to milder respiratory disease, irrespecti ve of the severity of the genotype.