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CDC releases recommendations for state newborn screening programs for cystic fibrosis

American Family Physician, April 15, 2005 by Matthew J. Neff

The Centers for Disease Control and Prevention (CDC) released recommendations on the screening of newborns for cystic fibrosis. The report includes an evaluation of the benefits and risks of this type of screening. It also provides recommendations on how to effectively implement screening programs for states that choose to routinely screen newborns for cystic fibrosis. The recommendations were published in the October 15, 2004, recommendations and reports series of Morbidity and Mortality Weekly Report. The full report is available online at http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5313a1.htm. An editorial discussing these guidelines also appears in this issue of American Family Physician on page 1482.

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In November 2003, the CDC and the Cystic Fibrosis Foundation (CFF) cosponsored a workshop to examine the benefits and risks of newborn screening for cystic fibrosis. The three objectives of the workshop were: (1) to review and evaluate the scientific evidence on the benefits and risks of newborn screening for cystic fibrosis; (2) to review screening, diagnostics, and follow-up concerns when making decisions about newborn screening for cystic fibrosis; and (3) to disseminate information about models and best practices for states that choose to adopt newborn screening for cystic fibrosis.

Evidence presented at the workshop supported the clinical utility of this type of screening. Demonstrated benefits include improved growth and cognitive development, reduced hospitalizations, and improved survival. Risks include psychosocial effects for carrier children and their families, and exposure of children to infectious agents through person-to-person transmission in clinical settings.

Background

Cystic fibrosis is the second most common life-shortening, childhood-onset inherited disorder in the United States, behind sickle cell disease. Annually, about 1,000 persons in the United States are diagnosed with cystic fibrosis. In 1979, a test to measure the levels of immunoreactive trypsinogen (which is substantially elevated in newborns with cystic fibrosis) in dried blood spots was introduced and made universal newborn screening for cystic fibrosis possible. This test is now the basis for newborn screening protocols.

In 15 to 20 percent of children with cystic fibrosis, the first symptom is meconium ileus; adverse outcomes include malnutrition, lung disease, and mortality. Because meconium ileus is diagnostic for cystic fibrosis, screening does not increase early detection for these children.

Early recognition of cystic fibrosis based on symptoms often is difficult because the majority of symptoms are not specific to the condition. Therefore, affected children are often diagnosed with celiac disease, food allergies, asthma, or bronchitis. The consequences of misdiagnosis include unnecessary diagnostic tests and hospitalizations, multiple office visits, cost to the health care system, and anxiety for parents.

The median age at diagnosis for all persons with cystic fibrosis in the United States is 5.3 months. The overall median age at diagnosis includes infants diagnosed soon after birth based on newborn screening, prenatal screening, family history, or the presence of meconium ileus. The median age at diagnosis based on signs and symptoms other than meconium ileus is 14.5 months, compared with 0.2 months in those with meconium ileus and 0.5 months for those receiving newborn screening. A diagnosis based on symptoms is associated with a more than twofold greater risk of medical complications before diagnosis than a diagnosis resulting from screening. Adverse psychosocial effects for the child's family also may result during the delay between the appearance of cystic fibrosis-related symptoms and diagnosis.

In 1999, a CFF consensus panel developed a new case definition for cystic fibrosis based on the following criteria: the presence of at least one characteristic phenotypic feature or a history of cystic fibrosis in a sibling or a positive newborn screening test, together with laboratory evidence of an abnormality in the gene that regulates expression of the cystic fibrosis transmembrane conductance regulator protein as documented by (1) elevated sweat chloride concentrations, (2) identification of two mutations associated with cystic fibrosis, or (3) in vivo demonstration of characteristic abnormalities in ion transport across the nasal epithelium. Sweat testing can be performed accurately on most infants at two to three weeks of age, but not all infants have sufficient quantities of sweat for reliable testing. Although a sweat chloride level of 60 mEq per L is diagnostic of cystic fibrosis, infants with cystic fibrosis often have initial sweat values of 30 to 59 mEq per L.

In 2000, approximately 400,000 children (10 percent) born in the United States were screened for cystic fibrosis, and this number was expected to increase to 800,000 in 2004. Screening protocols for cystic fibrosis are listed in the accompanying table.

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CDC releases recommendations for state newborn screening programs for cystic fibrosis

American Family Physician, April 15, 2005 by Matthew J. Neff

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