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Formal name: Stool or faecal trypsin and chymotrypsin
Related tests: Trypsinogen (IRT); faecal fat

At a Glance

Why Get Tested?

To screen for cystic fibrosis and pancreatic insufficiency by evaluating pancreas function

When to Get Tested?

When you or your newborn or infant has symptoms of pancreatic insufficiency or cystic fibrosis such as persistent diarrhoea, foul-smelling bulky greasy stools, malnutrition, and vitamin deficiency

Sample Required?

A fresh stool sample, uncontaminated with urine

The Test Sample

What is being tested?

Trypsin and chymotrypsin are proteolytic enzymes. Their job is to digest protein in the small intestine. Normally, their precursors (their inactive forms: trypsinogen and chymotrypsinogen) are produced in the pancreas and transported to the small intestine.

In the small intestine, trypsinogen is activated, turned into trypsin, by an enzyme in the intestinal mucosa and then trypsin in turn activates chymotrypsinogen to chymotrypsin. Together, they form powerful chemicals responsible for breaking down the protein in food into smaller pieces called peptides. Trypsin and chymotrypsin will be detectable in the small intestine and in the stool if the pancreas is functioning normally.

In people with cystic fibrosis, mucous plugs can block the pancreatic ducts that lead into the small intestines, preventing trypsinogen and chymotrypsinogen from reaching the intestines. These mucous plugs can also block small airway passages in the lungs making one susceptible to respiratory infections and chronic pulmonary disease. It is usually the respiratory complications of cystic fibrosis that eventually proves fatal for people with this disease.

In people with pancreatic tissue damage or blockages, there may be either blocked pancreatic ducts or the cells that produce trypsinogen and chymotrypsinogen may be damaged or destroyed. Such cell damage causes pancreatic insufficiency, as not enough of the enzymes reach the small intestine to digest food properly. This is often seen in conditions such as chronic pancreatitis and pancreatic cancer.

How is the sample collected for testing?

A fresh stool sample is collected, uncontaminated with urine. For an infant, a urine collection bag (with adhesive edges that can be stuck to the baby’s skin) and a plastic-lined nappy are both used. This is to keep urine out of the stool and to keep the stool from soaking into the nappy.

The Test

Common Questions

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.