Immunoreactive trypsin levels in young cystic fibrosis patients and in other sick children.

Immunoreactive trypsin (IRT) levels were measured in blood samples from 32 healthy adults, 21 CF heterozygotes, 36 non CF sick children and 32 young CF or, suspected CF, patients with the Hoechst RIA Gnost Trypsin assay kit and in some cases with the Cis Sorin trypsin RIA kit. IRT levels were similar in adult controls and CF heterozygotes. CF patient IRT levels were age related, decreasing from markedly elevated values in the first few months of life to subnormal levels at a later stage. Thus, this assay may be useful in the early detection of CF. However, as up to 25% of non CF sick neonates also had elevated IRT levels positive results should be interpreted with caution.