Screening for cystic fibrosis by died blood spot trypsin assay.

Immunoreactive trypsin was measured in dried blood specimens from 14,000 infants. A second test was performed in 0 . 2% of the population in whom blood trypsin levels were greater than 80 ng/ml. Five infants with cystic fibrosis were then detected, with only one case of persistent hypertrypsinaemia in whom this diagnosis could not be established. No false-negative test results have yet been identified. Seventeen infants with cystic fibrosis were tested inthe first 2 weeks of life, only one of whom had a blood trypsin concentration less than 80 ng/ml.