An evaluation of the first ten years of Newborn Screening for cystic fibrosis in Ireland

Abstract Ireland has the world’s highest incidence of cystic fibrosis (CF). Newborn screening for CF (NBSCF) improves outcomes but identifies carriers and may yield false positive/inconclusive results. This study aimed to evaluate the performance of the first 10 years of the Irish NBSCF programme. Data collected by the programme between 01st July 2011 and 30th June 2021 were analysed, including cases of CF, CF carriers and Cystic Fibrosis Screen Positive Inconclusive Diagnosis (CFSPID). Microsoft Excel was used to calculate sensitivity, specificity and positive predictive value (PPV). Results were compared to European Cystic Fibrosis Society (ECFS) standards. Overall 650,809 neonates were screened, with 290 cases of CF, 533 CF carriers and 21 CFSPIDs reported. NBSCF identified 284 (98%) of the children with CF, sensitivity was 97.93% (95% CI 96.29-99.57), specificity was 99.91% (95% CI 99.91-99.92%), PPV was 0.34 (95% CI 0.31-0.37). The observed incidence of CF was 1 in 2,203, still Europe’s highest. Of the six undetected cases, most were of Asian ethnicity, suggesting panel limitations for diverse ethnicities.The Irish NBSCF programme exceeded ECFS standards. Most false negatives were caused by CFTR mutations undetected by the genetic panel. Increasing the size of the genetic panel increases detection of CFSPID and carriers and is not currently recommended. Ongoing validity monitoring is vital as the Irish population diversifies. Key messages • The Irish Newborn Screening Programme for Cystic Fibrosis is effective. • Ongoing validity monitoring is vital as the Irish population diversifies.