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Neonatal cystic fibrosis screening test

Neonatal cystic fibrosis screening is a blood test that screens newborns for cystic fibrosis (CF). How the Test is Performed A sample of blood is either taken from the bottom of the baby's foot or a vein in the arm. A tiny drop of blood is collected onto a pie

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Neonatal cystic fibrosis screening is a blood test that screens newborns for cystic fibrosis (CF).

How the Test is Performed

A sample of blood is either taken from the bottom of the baby's foot or 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.

The blood sample is examined for increased levels of immunoreactive trypsinogen (IRT). This is a protein produced by the pancreas that is linked to CF.

How the Test will Feel

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

Why the Test is Performed

Cystic fibrosis is a disease that is usually passed down through families. CF causes thick, sticky mucus to build up in the lungs and parts of the digestive tract. It can lead to breathing and digestive problems.

Children with CF who are diagnosed early in life and start treatment at a young age may have better nutrition, growth, and lung function. This screening test helps health care providers identify children with CF before they have symptoms.

Some states include this test in the routine newborn screening tests that are done before the baby leaves the hospital.

If you live in a state that does not perform routine CF screening, your provider will explain whether testing is needed.

Other tests that look for genetic changes known to cause CF may also be used to screen for CF.

Normal Results

If the test result is negative, the child likely does not have CF. If the test result is negative but the baby has symptoms of CF, further testing will likely be done.

What Abnormal Results Mean

An abnormal (positive) result suggests that your child may have CF. But it is important to remember that a positive screening test does not diagnose CF. If your child's test is positive, more tests will be done to confirm the possibility of CF.

  • Sweat chloride test is the standard diagnostic test for CF. A high salt level in the person's sweat is a sign of the disease.
  • Genetic testing may also be done.

Not all children with a positive result have CF.

Risks

Risks associated with the test include:

  • Infection (a slight risk any time the skin is broken)
  • Anxiety over false positive results
  • False reassurance over false negative results

Alternative Names

Cystic fibrosis screening - neonatal; Immunoreactive trypsinogen; IRT test; CF - screening

Images

  • Infant blood sample

References

Egan ME, Schechter MS, Voynow JA. Cystic fibrosis. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics . 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 454.

Lo SF, Roper SM. Laboratory testing in infants and children. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics . 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 769.

Review Date 4/1/2024

Updated by: Charles I. Schwartz, MD, FAAP, Clinical Assistant Professor of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, General Pediatrician at PennCare for Kids, Phoenixville, PA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

Related MedlinePlus Health Topics

  • Cystic Fibrosis
  • Newborn Screening

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Source-derived material selected through this article’s indexed topics.

Related questions

01When to see a doctor

If you or your child has symptoms of cystic fibrosis — or if someone in your family has CF — talk with your healthcare professional about testing for the condition. Make an appointment with a doctor who has skills and experience in treating CF. CF requires regular follow-up with your healthcare professional, at least every three months. Call your healthcare professional if you have new or worsening symptoms, such as more mucus than usual or a change in the mucus color, lack of energy, weight loss, or severe constipation. Get medical care right away if you're coughing up blood, have chest pain or trouble breathing, or have severe stomach pain and bloating. Call 911 or your local emergency number or go to the emergency department at a hospital if: You're having a hard time catching your breath or talking. Your lips or fingernails turn blue or gray. Others notice that you're not mentally alert.

Source: www.mayoclinic.org ↗
02Is there anything else I need to know about a sweat test?

In rare cases, conditions other than CF may result in high chloride levels on a sweat test. These conditions include hypothyroidism , nephrogenic diabetes insipidus , and Addison disease .

Source: medlineplus.gov ↗
03Are There Any Special Steps Required to Get Alyftrek?

Alyftrek is a specialty medicine. This means that you can only get it from a specialty pharmacy and it may require prior authorization from your insurance company.

Source: www.webmd.com ↗
04What Are the Symptoms of Cystic Fibrosis?

The symptoms of cystic fibrosis vary. Some children will have symptoms at birth, while others may not have symptoms for weeks, months, or even years. The severity of symptoms also varies, with some children showing only mild digestive and lung problems and others having severe food-absorption problems and life-threatening breathing complications. The most common symptoms of cystic fibrosis are: Salty-tasting skin , which parents notice when they kiss their child Frequent coughing , wheezing , or bouts of pneumonia or sinusitis Difficulty breathing that keeps getting worse Big appetite but poor weight gain Bulky, smelly, greasy bowel movements Over time, the symptoms of cystic fibrosis can worsen and may include: Chronic productive cough, recurrent lung infections Obstructive lung disease ( emphysema ) Chronic nasal congestion and sinus infections Pancreatitis , a painful inflammation of the pancreas Liver disease Diabetes Gallstones

Source: www.webmd.com ↗
05What you can do

You might want to take a friend or family member with you to the appointment to help you remember information. Before your appointment, make a list of: Symptoms and when they started. Include anything that makes symptoms worse or better. All medicines, vitamins, herbs and supplements that you or your child take. Include the doses. Family history, such as whether anyone in your family has cystic fibrosis. Treatment you or your child have had for CF, if any. Include what the treatment was and if it helped. Any other medical conditions and their treatments. Questions to ask your healthcare professional. Questions to ask may include: What is likely causing these symptoms? What kinds of tests are needed? What treatment do you recommend? I or my child have other health conditions. How will cystic fibrosis affect them? Are there any limits needed? Feel free to ask other questions during your appointment.

Source: www.mayoclinic.org ↗
Research context

Read sources and limitations before applying a claim.

Research and Statistics: Who Has Cystic Fibrosis?

About 40,000 people are living with cystic fibrosis in the United States, and there are approximately 105,000 people with CF worldwide. (3) More than 75 percent of people with the disease are diagnosed by age 2, and more than half of all people living with cystic fibrosis are 18 or older. CF occurs predominantly in white populations, at a rate of 1 in 2,500 births. Between 2 and 5 percent of white people are carriers of the CFTR gene variant but have no overt clinical signs of disease. The disease is less common among African Americans, occurring at the much lower frequency of approximately 1 out of 17,000 births. (15) CF gene variants are most prevalent in persons of northern and central European ancestries or of Ashkenazi Jewish descent. They are rarely found in Native Americans, Asians, or native Africans. (16) CF is equally common among men and women, but women patients fare significantly worse than male patients with the disease. The median survival age for female CF patients is about three years younger than it is for men, but the reasons for the poorer survival rates among women are not completely understood. (17)

Source: everydayhealth.com ↗
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