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Cystic fibrosis |
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Condition: Cystic fibrosis
Cystic Fibrosis is an inherited disease, caused by a defective gene, which causes problems for the respiratory and digestive systems. Early detection can improve and lengthen life.
More technical information from the Mountain States Genetic Network:
Cystic fibrosis is an autosomal recessive disorder characterized by dysfunction of several exocrine systems. The incidence of cystic fibrosis is 1 in 2,500 Caucasian infants, somewhat lower among other ethnic groups.
Clinical Features:
The initial presentation may be in the neonatal period with meconium ileus or later in infancy or childhood with growth problems, malabsorption and malnutrition, and/or pulmonary disease. Severity of symptoms is variable. Death usually occurs between the second and fourth decades of life as a result of obstructive pulmonary disease and infection.
Laboratory Tests:
Elevation of immunoreactive trypsinogen (IRT) in a dried blood spot is the current screening method for CF. False positives and false negatives are known to occur, with false negatives occurring more frequently in neonates with meconium ileus.
Treatment:
Studies are inconclusive but evidence suggests that early detection and intervention may minimize the severity of the usual complications of CF. Specifically, pancreatic enzyme supplementation may minimize problems with malabsorption and malnutrition, while respiratory therapy may decrease pulmonary infections. Early detection also allows for genetic counseling and prenatal diagnosis for future pregnancies.
Screening Practice Considerations:
Elevations of trypsinogen decline after the first several months of life, so while exact timing of specimen collection in the neonatal period is not critical, the collection of the second screening specimen to follow-up an initial abnormal screen should occur no earlier than 21 days, to avoid an increased number of false positives, and no later than 60 days, to reduce the risk of false negatives. Use of the IRT test in older infants and children is not recommended; a sweat test is advised if CF is suspected in this older group. Sweat testing by personnel trained specifically in an accurate method is essential for proper diagnosis of cystic fibrosis.
The purpose of newborn screening is to identify infants at risk and in need of more definitive testing. As with any laboratory test, both false negative and false positive results are possible. Screening test results are insufficient information on which to base diagnoses or treatment
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