Cystic fibrosis screen positive inconclusive diagnosis (CFSPID) is a relatively common outcome of Cystic Fibrosis (CF) newborn screening (NBS). Infants with CFSPID do not have clinical features consistent with a diagnosis of CF and further research is needed to determine the prognosis and the best practices for management. Researchers of this project hypothesized a high prevalence of CFSPID infants and a different clinical management among centres involved. So they would retrospectively evaluate the prevalence, management and clinical outcome of CFSPID patients followed in 6 Italian CF centres from 01.01.2011 to 31.08.2018. However, a prospective assessment of CFSPID infants born in the period 01.09.2018-31.12.2019 will be carried out until 30.06.2020 in order to standardize the management. A high percentage of CFSPID infants and variable ratio CFSPID/CF among the centres involved, due to on NBS programs’ difference is expected; moreover a relevant different management of CFSPID infants in relation to the lack of comprehensive clinical data. The final objective is to know prevalence and clinical outcomes of CFSPID so that recommendations for diagnosis and treatment could be made.