Dried-blood spot screening for cystic fibrosis in the newborn.

Serum-immunoreactive-trypsin (I.R.T.) was measured in children with cystic fibrosis (C.F.) and a 
variety of controls. In the first few months of life all 
C.F. children had a raised serum-I.R.T. A dried blood-spot assay for 
I.R.T. was established and has potential as a screening test for 
C.F. in the newborn. 