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 it used?
The test is used to screen symptomatic newborns and infants for cystic fibrosis and to evaluate both children and adults for pancreatic sufficiency.
When is it requested?
The trypsin/chymotrypsin test is easy and non invasive. It is used as a screen for cystic fibrosis and pancreatic function. It is done when a newborn or infant has symptoms of cystic fibrosis such as persistent diarrhoea, foul-smelling bulky greasy stools, malnutrition and vitamin deficiency. It is also requested when a child or an adult has these symptoms, in order to help diagnose pancreatic insufficiency.
What does the result mean?
A positive result is normal, indicating the presence of trypsin and chymotrypsin in the stool. A negative result is not diagnostic, but it does indicate that further testing, both for pancreatic insufficiency and for cystic fibrosis, may be indicated. Other pancreas dysfunctions, such as acute and chronic pancreatitis, can cause negative results.
Is there anything else I should know?
If someone's pancreas is not functioning correctly, the individual will need to be monitored closely by his or her physician. He/she may find symptom relief and nutritional improvement by taking doctor-prescribed oral enzymes and vitamin supplements.
Common questions
Your doctor may request newborn immunoreactive trypsin testing (IRT), sweat chloride testing, and/or CF gene mutation testing.
Testing for faecal pancreatic elastase may sometimes be ordered. Your doctor may request a stool test for faecal fat or a blood test for amylase or lipase to look at other aspects of pancreas and digestive function.
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