20 Influence of gestational age and day of life on IRT and PAP in cystic fibrosis screening

Abstract

Objectives: The determination of immunoreactive trypsin (IRT) and pancreatitisassociated protein (PAP) in dried blood spots is one possibility of conducting a neonatal cystic fibrosis screening. In the present study we examined the influence of gestational age and day of life on IRT and PAP. Methods: Data from the newborn screening center of Dresden, Germany in the years from 2008 to 2010 were studied. IRT measurement was done with AutoDELFIA Kit (PerkinElmer Turku). PAP measurement with MucoPAP Kit (DYNABIO Marseille). All specimen were tested on IRT and for samples exceeding 50 ng/ml PAP measurement was added. For this study we analyzed all data of newborn screening cards which were taken in the age of 36−72 h after birth and contained information of gestational age. Results: 42,607 newborn screening results met the inclusion criteria. In 1889 cases determination of PAP was executed. While IRT showed a minor correlation to gestational age (r = −0.058, p< 0.001), PAP was strongly correlated to gestational age (r = 0.540, p< 0.001). PAP and IRT correlated strongly as well (r = 0.484, p< 0.001). Day of life showed only a minor correlation to IRT (r = −0.035, p< 0.001) and PAP as well (r = −0.050, p = 0.029). Conclusion: A severe influence of gestational age on IRT could not be seen while PAP was strongly affected. Therefore, borderline PAP results in preterm infants should be interpreted carefully. To avoid screening failure in preterm babies control samples and sweat testing should be initiated liberally even after completed 32 weeks of gestation (final time for other screenings).