[Screening in Cystic Fibrosis in the Chilean population. Pilot project for screening in newborns].

Neonatal screening has been implemented internationally with different protocols and has become the routine method in the preclinical stage. Late diagnosis is associated with more severe symptoms with decreased survival and higher treatment costs.

Objectives: To estimate the incidence of cystic fibrosis; to evaluate the performance of the screening algorithms Immunoreactive Trypsinogen and Pancreatitis-Associated Protein (IRT/PAP) and the IRTxPAP product; to analyze the cut-off value for IRT, PAP, and IRTxPAP, and to establish a methodology for its ongoing evaluation; finally, to evaluate the quality of IRT and PAP measurements.

Patients and method: a neonatal screening protocol was implemented using the IRT/PAP assays plus IRTXPAP product in a 7-year pilot study. Between 2015 and 2021, a total of 371,724 heel dried blood spot samples were collected in maternity and neonatology units from the public healthcare network in 17 hospitals in the Metropolitan Region (RM) and 15 in the Valparaíso Region (RV). 277,245 newborns met the inclusion criteria.

Results: with IRT/PAP plus IRT x PAP the incidence was 1/7,109 NB. The cut-off value and percentiles were established for IRT, PAP, IRT x PAP. The best sensitivity and specificity obtained by ROC analysis gave an IRT value of 48,142 ng/mL (98.8th percentile), PAP of 1.68 ug/L and IRT x PAP of 140ug2/L. The performance of the IRT/PAP detection algorithms, the IRT x PAP product, and the quality of measurements were evaluated.

Conclusion: The results allow us to report that the IRT/PAP plus IRTxPAP protocol can be implemented in Chile, complying with international guidelines, with adequate government funding.