Predictors of deterioration of lung function in cystic fibrosis.

The severity of lung disease in cystic fibrosis (CF) may be related to the type of mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, and to environmental and immunological factors. Since pulmonary disease is the main determinant of morbidity and mortality in CF, it is important to identify factors that can explain and predict this variation. The aim of this longitudinal study of the whole Swedish CF population over age 7 years was to correlate genetic and clinical data with the rate of decline in pulmonary function. The statistical analysis was performed using the mixed model regression method, supplemented with calculation of relative risks for severe lung disease in age cohorts.The severity of pulmonary disease was to some extent predicted by CFTR genotype. Furthermore, the present investigation is the first long-term study showing a significantly more rapid deterioration of lung function in patients with concomitant diabetes mellitus. Besides diabetes mellitus, pancreatic insufficiency and chronic Pseudomonas colonization were found to be negative predictors of pulmonary function. In contrast to several other reports, we found no significant differences in lung function between genders. Patients with pancreatic sufficiency have no or only a slight decline of lung function with age once treatment is started, but an early diagnosis in this group is desirable.

Three common CFTR mutations should be included in a neonatal screening programme for cystic fibrosis in Sweden.

Children with cystic fibrosis (CF) diagnosed by neonatal screening have a better nutritional development and other advantages compared with those in a nonscreened group. The two-tier immunoreactive trypsinogen (IRT)/DNA screening protocol has been found superior to the single-tier IRT approach, improving the positive predictive value and thus reducing the false-positive rate. However, variations of the DNA test are required for different populations. In this study we examined CFTR (cystic fibrosis transmembrane conductance regulator) mutations in 331 CF patients attending the centres in Stockholm, Lund and Uppsala, comprising about 75% of the CF population in Sweden. The frequency of deltaF508 among CF alleles was 68.3%. There were two other mutations, 394delTT and 3659delC, found to be fairly frequent, amounting to 8.5 and 7.9%, respectively. Other mutations were comparatively rare. A simple and effective method of analysing the three mutations from Guthrie cards has been developed. Assuming Hardy-Weinberg equilibrium, 90% of our CF patients will be expected to carry at least one deltaF508 allele and 97.6% to carry at least one deltaF508, 394delTT or 3659delC copy. Including the latter two in a screening programme would thus substantially reduce the risk of a false-negative outcome.