[Mucoviscidosis screening with immunoreactive trypsin]

Up to now 49,116 immunoreactive trypsin (IRT) measurements have been carried out in Austrian newborns in the first week of life. Related to provisionally chosen cut-off points, 301 newborns (0.61%) showed an elevated IRT value; 253 of them were successfully recalled. According to a direct strategy, sweat tests were done without a second IRT measurement in 101 infants; eleven of them were identified as cystic fibrosis (CF) patients. In accordance with a 2-step strategy, 152 infants were reinvestigated by a second IRT determination. Twenty-eight of them again showed an elevated IRT value, as based on provisional, age-dependent reference values; seven were subsequently identified as CF patients by sweat testing. So far two false-negative findings were obtained on IRT screening: one child was later identified as having CF on the basis of typical clinical symptoms and a positive sweat test, the other patient presenting with meconium ileus showed a normal IRT value after surgery, but was subjected to a sweat test in view of the underlying condition. These preliminary results suggest a CF incidence of 1 to 2460 newborns in Austria. Hence, IRT screening appears to be a reliable method for identifying CF patients in the newborn period, thereby facilitating early treatment and genetic counselling.