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Newborn Cystic Fibrosis Screening

Newborn cystic fibrosis (CF) screening is a blood test that looks for increased levels of an enzyme produced by the pancreas (immunoreactive trypsinogen, or IRT). The test is performed on newborn babies to screen for cystic fibrosis.

Newborn CF screening is recommended by many states (including New Hampshire), the national Cystic Fibrosis Foundation, and the Center for Disease Control (CDC). Early diagnosis of CF is important to improve the overall health of children with CF.

How the test is performed

  • A small sample of blood is typically taken from the baby's heel while they are still in the newborn nursery. The dried blood spot is sent to the New England Regional Newborn Screening Lab in Massachusetts.
  • If your child's blood sample has an abnormally high IRT value, the lab will do a second test on the same blood sample to look for the presence of a CF gene.

A CF newborn screening test is considered positive if:

  • Your child's blood sample has an abnormally high IRT value.
  • The secondary lab test detects at least one CF gene.

About one in ten children who have a positive CF newborn screening test will actually have cystic fibrosis.

A positive screen result requires followup testing, called a sweat test. This test will be performed at the CF Program in either Lebanon or Manchester.

If the CF newborn screening test is positive but the sweat test is negative:

  • Your child does not have CF, but is a carrier of the CF gene.
  • About one in 25 to 30 Caucasian people carry this CF gene.
  • Carriers are typically healthy people without symptoms of CF.
  • If your child is a carrier of the CF gene, further genetic counseling for your family will be important. The CF Program can set this up for you after your sweat test appointment.

If the CF newborn screening test is positive and the sweat test is positive:

  • We will do a second sweat test to double-check the results. If the second sweat test is positive:
  • Your child will be seen by a doctor and nurse who are specialists in the care of children with CF.
  • You will also eventually meet other health professionals who are on the CF team.
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