Why are newborns screened for Cystic Fibrosis?
The Cystic Fibrosis Foundation and the Centers for Disease Control and Prevention (CDC) recommend screen for Cystic Fibrosis (CF) in all newborns. More than 10 million Americans are carriers of the defective gene that causes CF and most are not aware of a family history of the disease. Research studies conducted over the past two decades have shown that early nutritional intervention is beneficial to improve height, weight, and cognitive function for people with CF. Early care also may impact respiratory function and life expectancy, and reduce hospitalizations.
Does a positive newborn screen mean that a baby has CF?
No, not necessarily. A newborn screening test is not a diagnostic test. In fact, only a fraction of babies with an initial positive CF newborn screening test ultimately are diagnosed with the disease. If an initial screen is positive, further tests are done to rule out or confirm a CF diagnosis.
What happens after a positive screen?
Your baby will have a Sweat Test. This is a test to determine whether your baby has CF. This test measures the amount of salt (sodium and chloride) in the sweat. Normally, sweat has very little sodium and chloride in it. In Cystic Fibrosis there is 2-5 times the normal amount of these chemicals in the sweat. The test is done in two steps. In the first step, a colorless, odorless chemical (known to cause sweating) is applied to two small areas on the arm or leg. An electrode is then attached to one of the areas. This electrode allows the technician to apply a weak electrical current to the area which causes sweating. There may be a tingling or warm feeling in this area. The electrode stays in place for about 5 minutes and will be repeated for the second area being tested. The second part of the sweat test involves cleaning the areas and collecting sweat on a piece of gauze or into a plastic coil. After thirty minutes, the collected sweat is sent to the laboratory for analysis. This entire process takes about one hour.
In general, a sweat chloride concentration less than 40mmol/L is normal, 41-59mmol/L is borderline, and 60mmol/L and above is positive for CF. The results of the sweat test will be available to the doctor by 4:00 pm on the afternoon of the day you complete the test. In some cases, the quantity of sweat obtained is not enough to give an accurate result. In this case, the test may need to be repeated. If the test falls into the “borderline” category (40-60mmol/L) repeat sweat tests or other diagnostic tests may be needed. If the test is positive, it will be repeated to confirm the diagnosis. You will receive a call from one of the CF team nurses with the test results. If you do not get a call, please call the office at 352-392-4458.
If your baby is diagnosed with cystic fibrosis, the CF Care Center team at the University of Florida (UF) will meet with your family to help you understand the disease and the care that is needed for your child. This team involves physicians, nurses, nutritionists, respiratory therapists, and social workers. It is important to have your child’s CF care managed by a care team at an accredited CF Center. If UF is not the center closest to your home, our team will help you get established with the right center for your needs.
If your child is a carrier of the CF gene or is diagnosed with CF, you will have a chance to talk with a genetic counselor so you will understand what this means to all the members of your family.
A word of caution…
The life and health of people with CF is much better than it was even a few years ago. If you wish to read more about CF, please go to the CF Foundation website for current and accurate information. If the diagnosis is positive, your care team will give you lots of current information and will be available to answer your questions.