WS11.3 Newborn screening for cystic fibrosis in Switzerland – performance after 4 years

Objectives Newborn screening (NBS) for cystic fibrosis (CF) was introduced in Switzerland in 2011, based on IRT-DNA-IRT protocol. It aims to detect all children with classical CF, but to avoid identifying children with equivocal disease, called "CF screen positive, inconclusive diagnosis" (CFSPID). Here we evaluate the program describing the proportion of false negatives and the detection of CFSPID. Methods We analysed data from the national CF screening database, including all children born between January 2011 and November 2014. Children with positive screening results were referred to a CF centre for a sweat test and faecal elastase. We assessed initial IRT tests, screening results and the final diagnoses of the children. In addition, we determined the proportion of false negatively screened children and calculated the ratio CF:CFSPID. Results Within 4 years, 338,851 IRT tests were performed. In total, 364 children were screened positive and referred to a CF centre for further examination. 98 children (27% of 364) were diagnosed with CF, 13 (4%) had CFSPID, 250 (69%) were found to have no CF, and 3 (1%) were lost to follow up. In addition, 6 children with a negative screening result were clinically diagnosed with CF (5.8% false negatives – 6/104), one of them because a second heel prick test was never taken. The ratio CF:CFSPID overall was 8:1 [2011 9:1 (28/3); 2012 4:1 (26/6); 2013 21:1 (21/1) and 2014 8:1 (23/3)]. Conclusion The Swiss newborn screening program for CF performed well. False negative results are in the expected range and the ratio CF:CFSPID is acceptable. However, to increase the CF:CFSPID ratio further monitoring and adaptations are required.