This is a test on the stool to screen for cystic fibrosis and pancreatic insufficiency by checking pancreas function. It is a test that may be done when you or your newborn or infant has symptoms of pancreatic insufficiency or cystic fibrosis such as persistent diarrhea, foul-smelling bulky greasy stools, malnutrition, and vitamin deficiency.
Trypsin and chymotrypsin are enzymes which digest protein in the small intestine. Normally, their precursors, 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 are 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 and pancreatic damage, these enzymes will not be made in large enough amounts to reach the small intestine to digest food properly.
PREPARATION FOR TEST
A fresh stool sample will be 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.
Your test should be positive. This is normal.
Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your doctor after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.
MEANING OF TEST
Your caregiver will go over the test results with you and discuss the importance and meaning of your results, as well as treatment options and the need for additional tests if necessary.
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.
OBTAINING THE TEST RESULTS
It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.