Trypsin and Chymotrypsin
In people with cystic fibrosis, mucous plugs can block the pancreatic ducts that lead into the small intestine, preventing trypsinogen and chymotrypsinogen from reaching the intestine. Similarly, mucous plugs can 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 prove fatal for patients with this disease.
Individuals with pancreatic dysfunction (tissue damage or blockage) may either have blocked pancreatic ducts or the cells that produce trypsinogen and chymotrypsinogen may be damaged or destroyed. Such cell damage causes pancreatic insufficiency, in which enzyme transport to the small intestine is inadequate for proper food digestion. 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 diaper are both used to keep urine out of the stool and to keep the stool from soaking into the diaper.
Is any test preparation needed to ensure the quality of the sample?No test preparation is needed.
How is it used?
When is it ordered?The trypsin/chymotrypsin test is easy and noninvasive. It is ordered when a newborn or infant has symptoms of cystic fibrosis such as persistent diarrhea, foul-smelling bulky greasy stools, malnutrition, and vitamin deficiency. It is also ordered 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, indicating the presence of trypsin and chymotrypsin in the stool, is normal. 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 physician. He may find symptom relief and nutritional improvement by taking doctor-prescribed oral enzymes and vitamin supplements.
What other tests might my doctor do to check for cystic fibrosis?
What other laboratory tests may be done if I or my child has a negative trypsin test?