Neonatal cystic fibrosis screening

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Infant blood sample

Neonatal cystic fibrosis screening is a blood test that looks for increased levels of immunoreactive trypsinogen (IRT), an enzyme produced by the pancreas. The test is performed on newborns to diagnose cystic fibrosis (CF).

Cystic fibrosis screening - neonatal; Immunoreactive trypsinogen; IRT test 

A sample of blood is either taken from the bottom of the baby's foot of a vein in the arm. A tiny drop of blood is collected onto a piece of filter paper and allowed to dry. The dried blood sample is sent to a lab for analysis.

Your health care provider will explain the test to you, and you must sign a consent form before the test. Some states, but not all, include this test in the newborn screening exams that are done before the mother and baby leave the hospital. 

The brief feeling of discomfort will probably cause your baby to cry.

Infants who have CF may have increased levels of IRT in their blood for several months after birth. A positive IRT test requires follow up testing to confirm the diagnosis.

Review Date: 05/16/2005
Reviewed By: John Goldenring, M.D., MPH, Department of Pediatrics, Children's Hospital, San Diego, CA. Review provided by VeriMed Healthcare Network.