Immunoreactive trypsin on dried-blood spots as a possible neonatal test for cystic fibrosis. (I. Evaluation of the method and preliminary field trial).

A method for blood spot immunoreactive trypsin (IRT) determination suitable for neonatal mass screening, and the preliminary steps towards its large-scale application are described. The method showed a highly significant correlation between blood spot and plasma values, and a study of plasma reference values in a population of 1,050 newborn infants demonstrated a log-normal distribution with a mean IRT concentration of 238.3 ng/ml. The results and their implications for neonatal mass screening are discussed.