Prospective Study of the Phenotypic Expression of Cystic Fibrosis (CF) Screened Positive Newborns With an Atypical Form of CF (DPAM)

The strategy of neonatal screening for Cystic Fibrosis in France relies on Immuno Reactive Trypsinogen (IRT) at day 3/DNA analysis with a CF Elucigen 30 mutations kit/ IRT safety-net at day 21. This strategy has significantly improved the performance of CF neonatal screening (NNS) in terms of positive predictive value and sensitivity but revealed new difficulties. Up to 85-90% of CF patients detected through the NNS program has a classical CF form with a positive sweat test and 2, 1 or no CF causing mutations but the remainder has either 2 CFTR mutations with at least one non-CF causing mutation and a sweat test \<60mmol/L or 1, 0 CFTR mutation and an intermediate sweat test value ≥ 30 et \< 60mmol/L raising a diagnosis and prognosis dilemma. Meanwhile the vast majority of these cohorts will remain asymptomatic over time, some will develop symptoms prompting clinicians to maintain a rigorous surveillance for the entire atypical cohort, whose modalities vary a lot among centers and countries. This prospective multicenter study with a standardized assessment of a matched cohort with "atypical" CF versus "classical" CF from 6 years of age (60-65 cases in each cohort) is aimed at evaluating pulmonary and nutritional status to, better define the best monitoring follow-up, therapeutic management and familial genetic counseling.