[Screening of newborn infants for cystic fibrosis. A combined analysis of immunoreactive trypsin and delta F508 mutation--a screening without false positive results].

A total of 1081 blood screening cards taken from newborn babies, were anonymously selected for cystic fibrosis (CF) screening by quantitation of immunoreactive trypsin (IRT, Delfia) and by delta F508 mutational analyses using polymerase chain reaction followed by a time resolved fluorescence hybridization assay (Delfia). The IRT values showed a log normal distribution and were significantly higher in girls than boys and in 28 carriers compared with 1052 normals. In 12 newborns, corresponding to 1.02%, an IRT concentration greater than 70 micrograms/l was found. One of these was a delta F508 homozygote with an IRT concentration of 380 micrograms/l. delta F508 mutational analyses showed 1052 normals, 28 heterozygotes, and one homozygote, i.e., a carrier frequency of this mutation for delta F508 of 1:39. In future newborn CF-screening programmes we therefore recommend Delfia IRT followed by Delfia delta F508 analyses for IRT values greater than 70 micrograms/l.