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Trypsinogen

Also known as: Trypsin-like immunoreactivity, Serum trypsinogen
Formal name: Immunoreactive trypsin (IRT)
Related tests: Stool trypsin, Sweat Chloride, CF gene mutation
The Test
 
How is it used?
When is it ordered?
What does the test result mean?
Is there anything else I should know?

How is it used?
Immunoreactive trypsin (IRT) is used as part of a newborn screening program to screen for an increased risk of cystic fibrosis and is used to help diagnose pancreatic insufficiency in both children and adults.



When is it ordered?
This test is ordered as part of a newborn screen for cystic fibrosis, in cases of meconium ileus (no stools in the first 24 to 48 hours of life), and as an initial test for cystic fibrosis in symptomatic young infants who are not creating enough sweat to do a sweat chloride test. A trypsinogen test is also ordered when children or adults present with symptoms suggesting cystic fibrosis and pancreatic dysfunction such as persistent diarrhea, foul-smelling bulky greasy stools, malnutrition, and vitamin deficiency.

Trypsinogen testing is not diagnostic; there are a fair number of false positives and problems other than CF and pancreatic dysfunction that can cause a positive IRT. An elevated level must be followed with other testing. When diagnosing CF, this may include another IRT in a month, CF gene mutation testing, and/or sweat chloride testing.



What does the test result mean?
NOTE: A standard reference range is not available for this test. Because reference values are dependent on many factors, including patient age, gender, sample population, and test method, numeric test results have different meanings in different labs. Your lab report should include the specific reference range for your test. Lab Tests Online strongly recommends that you discuss your test results with your doctor. For more information on reference ranges, please read Reference Ranges and What They Mean.

If an IRT level is elevated, an infant may have cystic fibrosis; an infant or adult may have abnormal pancreatic enzyme production, pancreatitis, or pancreatic cancer; or the elevated IRT may be a false positive. Elevated levels need to be followed with further testing. If the IRT level is negative but the infant is symptomatic, other testing for CF, such as sweat chloride and/or CF gene mutation testing, should be considered.


Is there anything else I should know?
IRT testing will not identify heterozygous carriers of a CF mutation. Their trypsinogen production and function will not be affected. In patients who do have CF, the degree of IRT elevation does not reflect the severity of the disease.





This article was last reviewed on January 23, 2006.
 
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