Newborn screening for Cystic Fibrosis was initiated in Indiana in the fall of 2007 and since then has allowed for early diagnosis of many infants in the state. These infants are currently being managed in Cystic Fibrosis Foundation accredited Centers and Programs and have had the advantage of new nutritional and respiratory treatments instituted at this very critical early age.
Explanation of How the Testing is Done
The primary care practitioner is the first link in identifying these infants. The positive newborn screening test will be generated after an initial high immunoreactive trypsinogen (IRT) reading on the Guthrie card dictates a checking of the CF panel for gene mutations. This panel of about 40 mutations should identify about 95% or more of the most common genes seen in the Indiana population. A positive test for one mutation will usually indicate that the infant is a carrier of CF but will represent disease in about 5% of these screens. The next step in these infants should be referral to a CFF accredited lab for sweat chloride testing. An infant who screens positive for two mutations has a presumptive diagnosis of CF and should be referred to a CFF accredited CF Center or Program. Rarely an infant is noted to have a very high IRT and the gene panel is negative. These infants will be noted to require observation for signs and symptoms of CF but at this time do not necessarily warrant further testing.
Newborn Screening May Not Identify Everyone with CF
It is important to remember NBS is just that- screening, and may not identify all infants with cystic fibrosis. It is well recognized that false negative screens may occur in infants with meconium ileus or plug and therefore close observation or further testing may be warranted in these infants. Primary care providers should continue to send patients with clinically significant signs and symptoms of CF for more definitive testing such as sweat chloride testing by pilocarpine iontophoresis or to a CFF accredited Center regardless of a negative test in the newborn period.