Neonatal screening for cystic fibrosis in Wales and the West Midlands: clinical assessment after five years of screening. Cystic fibrosis mutations and genotype-pulmonary phenotype analysis.
Screening of the newborn for cystic fibrosis by measurement of immunoreactive trypsin has been undertaken on alternate weeks in Wales and the West Midlands for five years since 1985 to evaluate the possible clinical benefits of early diagnosis. Patients detected by screening and those diagnosed by clinical symptoms alone were assessed annually for differences in clinical, anthropometric, and biochemical variables. Fifty eight infants not considered to be at risk of cystic fibrosis (they did not present with meconium ileus and do not have a sibling with cystic fibrosis) have been detected by screening and they have been compared with 44 children who were diagnosed clinically. This latter group includes nine children whose screening was negative but who were recognised subsequently to have cystic fibrosis. The mean age at diagnosis of the screened group was significantly lower than that of the group diagnosed clinically. Excluding admissions for diagnostic tests for cystic fibrosis, the screened group spent a significantly shorter time in hospital during the first year of life. The results of all other comparisons made between the screened group and those diagnosed clinically were similar up to the age of 4 years. Although there are more than 1000 mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, most of them are uncommon and only limited information exists regarding genotype-pulmonary phenotype relationships.
                We determined and classified the CFTR mutations using denaturing high-performance liquid chromatography and developed new, quantitative methods to categorize pulmonary phenotypes.
                Two novel alleles were discovered, namely G1047R and 1525-2A-->G, which were accompanied by F508del and G551D mutations, respectively. Assessment of numerous options revealed that CF pulmonary phenotype categorization in children cannot be accomplished with clinical or pulmonary function data but is facilitated by longitudinal quantitative chest radiology. It was most useful to categorize pulmonary disease status by evaluating the typical pattern of abnormalities in patients homozygous for the F508del mutation, and then compare patients with minor mutations to this typical CF pulmonary phenotype. By this method, both patients with novel mutations have pulmonary phenotypes typical of F508del homozygotes. However, patients with class IV mutations (e.g., R347P) or with pancreatic sufficiency showed serial chest radiographs that were atypically mild.
                Longitudinal quantitative chest radiography provides a new strategy for CF pulmonary phenotype categorization that should be useful for genotype-phenotype delineation in individual patients and in both epidemiologic studies and clinical trials involving groups of children with CF.
Two randomised controlled trials assessing neonatal screening in CF were identified; data from one study were included. Nutritional benefits are apparent. Screening provides potential for better pulmonary outcomes, but confounding factors influenced long-term pulmonary prognosis of people with CF. Screening seems less expensive than traditional diagnosis.