Single-centre prospective evaluation of the first 5 years of cystic fibrosis newborn screening in Germany

Background In 2016, nationwide cystic fibrosis newborn screening (CFNS) was newly implemented in Germany, using an immunoreactive trypsin/pancreatitis-associated protein/DNA screening algorithm that differs from most other nationwide screening programmes. Methods We analysed real-life feasibility of the confirmation process with respect to our pre-specified procedural objectives. These included overall accuracy through false-negative and false-positive results, effectiveness of the Bavarian tracking system, and accuracy of Macroduct and Nanoduct sweat conductivity compared with quantitative chloride determination. All consecutive CFNS-positive newborns assigned to our CF centre and born between 1 September 2016 and 31 August 2021 (n=162) were included. Results The German CFNS was feasible at our CF centre as all procedural objectives were met. The positive predictive value (PPV) of positive CFNS was low (0.23) and two initially negatively screened children were later diagnosed with CF. The tracking system was highly efficient with a 100% tracking rate. The Macroduct and Nanoduct systems had comparable success rates (93.2% versus 95.9%). Importantly, conductivity via Macroduct was more accurate than via Nanoduct (zero and four false-positive newborns, respectively). Conclusions CF confirmation diagnostics of neonates in a certified regional CF centre was well managed in daily routine. The PPV of the German CFNS needs to be improved, e.g. by extending the DNA analysis within the screening algorithm and by increasing the number of variants tested. The Bavarian tracking system can serve as a successful model for other tracking systems. We preferred the Macroduct system because of its more accurate sweat conductivity readings.