Prospective and parallel assessments of cystic fibrosis newborn screening protocols in the Czech Republic: IRT/DNA/IRT versus IRT/PAP and IRT/PAP/DNA
Abstract
Cystic fibrosis (CF) is a life-threatening disease for which early diagnosis following newborn screening (NBS) improves the prognosis. We performed a prospective assessment of the immunoreactive trypsinogen (IRT)/DNA/IRT protocol currently in use nationwide, versus the IRT/pancreatitis-associated protein (PAP) and IRT/PAP/DNA CF NBS protocols.
Dried blood spots (DBS) from 106,522 Czech newborns were examined for IRT concentrations. In the IRT/DNA/IRT protocol, DNA-testing was performed for IRT a parts per thousand yenaEuro parts per thousand 65 ng/mL.
Newborns with IRT a parts per thousand yenaEuro parts per thousand 200 ng/mL and no detected cystic fibrosis transmembrane conductance regulator gene (CFTR) mutations were recalled for a repeat IRT. In the same group of newborns, for both parallel protocols, PAP was measured in DBS with IRT a parts per thousand yenaEuro parts per thousand 50 ng/mL.
In PAP-positive newborns (i.e., a parts per thousand yen1.8 if IRT 50-99.9 or a parts per thousand yen1.0 if IRT a parts per thousand yenaEuro parts per thousand 100, all in ng/mL), DNA-testing followed as part of the IRT/PAP/DNA protocol. Newborns with at least one CFTR mutation in the IRT/DNA/IRT and IRT/PAP/DNA protocols; a positive PAP in IRT/PAP; or a high repeat IRT in IRT/DNA/IRT were referred for sweat testing.
Conclusion: the combined results of the utilized protocols led to the detection of 21 CF patients, 19 of which were identified using the IRT/DNA/IRT protocol, 16 using IRT/PAP, and 15 using IRT/PAP/DNA. Decreased cut-offs for PAP within the IRT/PAP protocol would lead to higher sensitivity but would increase false positives.
Within the IRT/PAP/DNA protocol, decreased PAP cut-offs would result in high sensitivity, an acceptable number of false positives, and would reduce the number of DNA analyses. Thus, we concluded that the IRT/PAP/DNA protocol would represent the most suitable protocol in our conditions.