Background: In cystic fibrosis newborn screening (CFNBS), immunoreactive trypsinogen (IRT) and pancreatitis-associated protein (PAP) can be used as screening parameters. We evaluated the IRT×PAP product as second-tier parameter in CFNBS in newborns with elevated IRT.
Methods: Data on 410,111 screened newborns including 78 patients with classical cystic fibrosis (CF) from two European centers were retrospectively analyzed by discrimination analysis to identify a screening protocol with optimal cutoffs. We also studied differences in PAP measurement methods and the association of IRT and PAP with age.
Results: PAP values differed systematically between fluorometric and photometric assays. The IRT×PAP product showed better discrimination for classical CF than PAP only as second-tier screening parameter (p<0.001). In CF patients, IRT decreased while PAP values remained high over years. In newborns without CF, IRT decreased after birth over weeks while PAP increased within days.
Conclusions: The IRT×PAP product performs well as second-tier cutoff parameter for CFNBS. Screening quality parameters depend on the analytic method and on age at blood collection.
Keywords: Cutoff; Cystic fibrosis; Immunoreactive trypsinogen; Newborn screening; Pancreatitis-associated protein.
Copyright Â© 2016 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.