Sweat Testing
Key to Early CF Diagnosis
Specialists in the Antonio J. and Janet Palumbo Cystic Fibrosis (CF) Center at Children's Hospital of Pittsburgh of UPMC want pediatricians who receive abnormal CF screening results for patients in their care to call the CF Center's nurse coordinator at 412-692-6107. Daniel Weiner, MD, associate director of Children's Hospital's CF Center, says that in Pennsylvania, there is not a standard as to where newborn screening results are sent. And often, when the pediatrician or obstetrician does receive the screening results, he or she may be uncertain as to what should be done.
Lavonne Bihler administers a sweat test to 7-month-old Allison Kelly, and conducts lab tests afterwards.
Whether the screening results suggest the child has cystic fibrosis or is an unaffected carrier of the gene, capable of passing it to offspring, the specialists at Children's can help with next steps.
In screenings that are indicative of CF disease, Children's specialists will coordinate and conduct sweat testing. The sweat test measures the amount of sodium and chloride in the child's sweat. Sweat tests can be done at any age, especially in babies weighing more than 7 pounds (smaller babies may not produce enough sweat to analyze).
Early diagnosis of CF allows for immediate intervention, which in turn has been shown to result in improved height, weight and cognitive function, and which also may help maintain respiratory function, increase life expectancy and reduce hospitalizations.
When the screening shows that the child is a carrier of an altered CF gene, Children's specialists can refer the child and family for genetic counseling. Such counseling is important for the entire family—newborn, siblings, as well as parents.
Contact the nurse coordinator at Children's Cystic Fibrosis Center at 412-692-6107.
Newborn Screening for Cystic Fibrosis: The Basics
Newborn screening for CF begins with determining the level of immunoreactive trypsinogen (IRT) in a dried blood spot. If the IRT is elevated, genetic analysis is performed to look for mutations in the CF gene (CFTR). However, there are more than 1,500 described mutations in CFTR and only the most common are included in the initial screening panel, meaning that further testing frequently is required.
- Since CF is a recessive disease, two altered CFTR genes
must be present. The most common mutation (DF508) is present in approximately 70 percent of abnormal CF chromosomes, and approximately 50 percent of CF patients have two copies of this mutation.
- A carrier has one copy of an altered CF gene. He or she does not have the disease but has a 50 percent chance of passing on the mutation to offspring. If both parents are carriers, there is a 25 percent chance with each pregnancy of having a child with cystic fibrosis.
