Trypsinogen

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Also known as: Trypsin-like Immunoreactivity; Serum Trypsinogen; IRT
Formal name: Immunoreactive Trypsinogen

At a Glance

Why Get Tested?

To detect cystic fibrosis (CF) and pancreatic insufficiency by evaluating pancreatic function

When to Get Tested?

As part of a newborn screening test; when a newborn has meconium ileus; or when someone has symptoms of pancreatic insufficiency such as persistent diarrhea, foul-smelling bulky greasy stools, malnutrition, and vitamin deficiency

Sample Required?

A blood sample drawn from an infant's heel, a spot of blood that is put onto filter paper, or a blood sample drawn from a vein in the arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

Trypsinogen is a pancreatic proenzyme, an inactive precursor to the enzyme trypsin. Normally, trypsinogen is produced in the pancreas and transported to the small intestine. In the small intestine, it is activated and turned into trypsin by an enzyme in the intestinal mucosa. Trypsin is responsible for breaking down the protein in food into smaller pieces called peptides. Without sufficient trypsinogen and trypsin, a person will not be able to properly digest and use proteins. Any condition that prevents trypsinogen from reaching the small intestine may cause an increase in trypsinogen in the blood. This test measures the amount of trypsinogen in the blood.

In people with cystic fibrosis (CF), mucous plugs can block the pancreatic ducts that lead into the small intestine, preventing trypsinogen from reaching the intestine and preventing the breakdown of food proteins. As part of a group of newborn screening tests, infants are screened for CF using a trypsinogen test called immunoreactive trypsinogen (IRT). Those newborns with CF may have elevated levels of IRT in their blood for several months, whereas in normal infants, any temporary false-positive elevations in trypsinogen will usually fall to normal low levels within a few weeks.

Pancreas tissue damage in other diseases, such as chronic pancreatitis and pancreatic cancer, may cause blockages that prevent trypsinogen from reaching the small intestine. The cells that produce trypsinogen can also become damaged or be destroyed, decreasing the body's supply. Both blockages and cell damage can cause pancreatic insufficiency.

How is the sample collected for testing?

A blood sample is drawn from a newborn's or very young infant's heel, a spot of blood is put onto filter paper, or a blood sample is drawn from a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

Common Questions

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Article Sources

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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.

Sources Used in Current Review

Kaneshiro, N. (Updated 2012 May 16).Neonatal cystic fibrosis screening. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003409.htm. Accessed September 2012.

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Dugdale, D. (Updated 2011 February 4). Trypsinogen test. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003560.htm. Accessed September 2012.

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Timothy S. Uphoff, Ph.D., D(ABMG), MLS(ASCP)CM.  Section Head Molecular Pathology Laboratory, Marshfield Labs, Marshfield Clinic, Marshfield WI.

Sources Used in Previous Reviews

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Denise I. Quigley, PhD, FACMG. Co-Director Cytogenetics/Molecular Genetics, Airport Way Regional Laboratory, Portland, OR.

Peter Jacky, PhD, FACMG. Director of Cytogenetics and Molecular Genetics, Airport Way Regional Laboratory, Portland, OR.