Immunoreactive trypsinogen

Measurement of immunoreactive trypsinogen (IRT) in blood of newborn babies is an assay in rapidly increasing use as a screening test for cystic fibrosis (CF). Measurement of immunoreactive trypsinogen (IRT) in blood of newborn babies is an assay in rapidly increasing use as a screening test for cystic fibrosis (CF). In CF, there is poor release from pancreatic ducts. Trypsinogen is a pancreatic enzyme precursor found in the blood that is raised in most of those with CF at birth, regardless of whether their mutation is pancreatic sufficient or insufficient. The concentration of IRT is elevated in babies with CF since pancreatic ducts are partially blocked leading to abnormal enzyme drainage. This occurs even if infants are pancreatic sufficient. Heterozygous carriers of cystic fibrosis can cause a raised IRT and it is therefore not diagnostic in isolation.