At a glance
Also known as
Trypsin-like immunoreactivity; serum trypsinogen, IRT
Why get tested?
To screen for cystic fibrosis (CF) in new-born infants
When to get tested?
It forms part of the newborn screening programme.
When a newborn infant has signs and symptoms of cystic fibrosis particularly meconium ileus (no stools in the first 24 to 48 hours of life) or where there is a high risk of the baby having the condition
A spot of blood drawn from the infant’s heel and put onto filter paper
Test preparation needed?
What is being tested?
Trypsinogen is a proenzyme, an inactive precursor to the trypsin. Normally, trypsinogen is produced in the pancreas and transported to the small intestine. In the small intestine, it is activated, turned into trypsin by an in the intestinal mucosa, forming a powerful chemical responsible for breaking down the in food into smaller pieces called peptides.
In babies with cystic fibrosis, mucous plugs can block the pancreatic ducts that lead into the small intestines, preventing trypsinogen from reaching the small intestine and resulting in a build-up of trypsinogen in the blood.
As part of the newborn screening programme infants are screened for cystic fibrosis using a trypsinogen test called immunoreactive trypsinogen (IRT). Several factors other than cystic fibrosis can affect the test result and therefore not all babies with high IRT will have cystic fibrosis. Where an elevated level is obtained, further investigation either by sweat testing or genetic analyses may be required.
How is the sample collected for testing?
A blood sample is taken by pricking a newborn's or very young infant's heel and a spot of blood is put onto filter paper.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.