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Newborn screening for cystic fibrosis in Switzerland--consequences after analysis of a 4 months pilot study
Toni Torresani1, Ralph Fingerhut, Corina S Rueegg
1Swiss Newborn Screening Laboratory, University Children's Hospital, Zürich, Switzerland.
Insights
Switzerland
Area of Science:
- Biochemistry
- Genetics
- Pediatrics
Background:
- Switzerland implemented newborn screening for cystic fibrosis (CF) in 2011.
- The screening utilized an immunoreactive trypsinogen (IRT)/DNA/IRT protocol.
- This study evaluates the initial year of screening, comparing protocol variations.
Purpose of the Study:
- To compare two versions of the CF NBS protocol with differing IRT cut-offs.
- To assess the impact of these changes on recall rates, sensitivity, and specificity.
- To optimize the NBS protocol for CF detection in Switzerland.
Main Methods:
- Two IRT cut-off thresholds were used: >45 ng/ml (99.0th percentile) and >50 ng/ml (99.2nd percentile).
- Recalls were omitted in the second period if IRT was <60 ng/ml and no common CF mutations were detected.
- Data from 26,535 (period 1) and 56,663 (period 2) tests were analyzed.
Main Results:
- Recall rates significantly decreased from 0.94% to 0.48% (p<0.001).
- Positive Predictive Value (PPV) improved from 23% to 47% (p=0.024).
- Sensitivity remained high, at 90% in period 1 and 100% in period 2.
Conclusions:
- Increasing the IRT cut-off and refining recall criteria reduced recall rates effectively.
- The modified protocol maintained high sensitivity for cystic fibrosis detection.
- This optimization enhances the efficiency of newborn screening for CF in Switzerland.
Background:
Switzerland introduced newborn screening (NBS) for CF in 2011, using an IRT/DNA/IRT protocol. This paper describes the results of the first year and compares two versions of the protocol with different IRT cut-offs, particularly effects on recall rate, sensitivity and specificity.
Methods:
IRT cut-offs were >45 ng/ml (99.0th percentile) in period 1 (months 1-4) and >50 ng/ml (99.2nd percentile) in period 2 (months 5-12). In period 2 we abstained from recalls when none of the 7 most common CF mutations were detected and IRT was <60 ng/ml.
Results:
In periods 1 and 2, 26,535 and 56,663 tests were performed. Recall rates were 0.94% and 0.48%, respectively (p<0.001), PPV increased from 23% to 47% (p=0.024) and sensitivity was 90% and 100%.
Conclusions:
Raising initial IRT cut-off from the 99.0th to the 99.2nd percentile and abstaining from recalls for children with an IRT<60 ng/ml and carrying no major CFTR mutation significantly reduced the recall rate without affecting sensitivity.
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