Cystic Fibrosis Genotype and Assessing Rates of Decline in Pulmonary Status

To evaluate the hierarchical phenotypic expression of cystic fibrosis transmembrane conductance regulator (CFTR) genotypes in the respiratory system as has been documented in the pancreas. This study was institutional review board approved; informed consent was not required. HIPAA guidelines were followed. Genotype effects were assessed by using chest radiographic and pulmonary function test (PFT) results in 93 patients. Serial chest radiographic and PFT (percentage of predicted forced expiratory volume in 1 second [FEV(1)], percentage of predicted forced vital capacity [FVC]) results were compared by using analysis of variance with repeated measures. By using CFTR class of mutations, two groups were created: group S (severe disease) and group M (mild disease). Within group S, three subgroups were created: A consisted of patients with two class I alleles; B, class I allele and class II or III allele; C, class II allele and class II or III allele. Group M consisted of patients with at least one allele from class IV-VI. Within group S, subgroup A had a faster deterioration than B or C according to radiographic data (A vs B, P = .014; A vs C, P = .009), with only a borderline difference in FEV(1) for subgroups A versus C (P = .031). Otherwise, PFTs were not sensitive for distinguishing subgroups. Only radiographic results identified that subgroup B had faster progression than C (P = .003); all parameters had trends of decline in the same direction. Group S had a faster decline than group M (radiography, P = .005; FVC, P = .011; FEV(1), P = .529). Disease progressed more rapidly with gene class hierarchical correlations seen in pancreatic disease. Radiography was more sensitive for identifying differences.