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. This is often seen in conditions such as chronic pancreatitis and pancreatic cancer; such cell damage causes pancreatic insufficiency, in which not enough of the enzymes reach the small intestine to digest food properly.
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 to keep urine out of the stool and to keep the stool from soaking into the nappy.
The Test
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 noninvasive. 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 test 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. S/he may find symptom relief and nutritional improvement by taking doctor-prescribed oral enzymes and vitamin supplements.
Common Questions
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Article Sources
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.
