Sensitive trypsin assay for dried-blood specimens as a screening procedure for early detection of cystic fibrosis.

An immunoreactive-trypsin assay uses small dried-blood spots (diameter 1.25 mm) and is 
therefore suitable for incorporation in established neonatal screening schemes. Blood specimens 
from neonates with cystic fibrosis had trypsin levels greater than those 
in control subjects, thus confirming earlier findings. Trypsin levels were below 
normal in several older patients with cystic fibrosis. 