Combining immunoreactive trypsinogen and pancreatitis-associated protein assays, a method of newborn screening for cystic fibrosis that avoids DNA analysis.

Objectives: To evaluate the performance of a strategy in which, after immunoreactive trypsinogen (IRT) determination, genetic analysis is replaced by a biological test, the pancreatitis-associated protein (PAP) enzyme-linked immunosorbent assay (ELISA).

Study Design: The French newborn screening program includes cystic fibrosis (CF) screening by the IRT/CFTR mutation strategy. PAP was assayed on screening cards, in parallel with IRT, in all newborns from 5 French regions (n = 204,749). Analysis of PAP values in CF and non-CF newborns with elevated IRT allowed direct comparison between the current strategy and the proposed IRT/PAP strategy.

Results: A protocol in which newborns with IRT >50 ng/mL and PAP >1.8 ng/mL and those with IRT >100 ng/mL and PAP >1.0 ng/mL are directly recalled for sweat testing would have the same performance as the IRT/CFTR mutation strategy.

Conclusions: The IRT/PAP strategy is an alternative for CF newborn screening, which avoids the drawbacks of genetic analysis and is cheaper and easier to implement than the current IRT/CFTR mutation strategy.