[Mucoviscidosis screening by determination of immunoreactive trypsin].

Immunoreactive trypsin (IRT) was measured radioimmunologically in samples of blood dried on filterpaper of 18 417 newborns. In 221 samples (1.2%) the concentration exceeded 80 ng/ml whole blood. In these cases we asked for a further sample of blood dried on filterpaper and for further clinical tests. Cystic fibrosis (CF) was confirmed in three babies, one of these died from meconium ileus. The IRT-concentrations did not drop significantly in 4 and 6 weeks respectively in the 2 patients, whereas this was the case in 192 babies without CF. Our data suggest that the determination of IRT may be developed into a highly specific screening method for CF provided that optimal reagents are selected and that blood is collected during the 4th or 5th week of life.