Data shows a declining incidence of cystic fibrosis since introduction of prenatal carrier screening
February 28, 2008
A study led by researchers at the New England Newborn Screening Program (NENSP) of the University of Massachusetts Medical School, and at Children's Hospital Boston, provides what may be the first population-based demonstration in the U.S. of a decline in the number of babies born with a genetic disease after the introduction of prenatal carrier screening. Their brief report, which links data from two independent population-based screening programs, appears in the February 28, 2008, New England Journal of Medicine.
The state of Massachusetts has offered universal newborn screening to detect cystic fibrosis (CF) since 1999. Newborn screening for cystic fibrosis (much like newborn screening for other conditions) is a public health service geared toward early diagnosis and referral of infants for diagnostic evaluation and care, as well as tracking the numbers of infants who are diagnosed with the disease.
Independently, recommendations for nationwide (adult) prenatal carrier screening for CF were introduced in the U.S. around 2002, coming from the National Institutes of Health, the American College of Obstetrics and Gynecology and the American College of Medical Genetics.
Using the Massachusetts newborn screening data, the researchers compared two four-year periods: 1999 to 2002, just before prenatal CF carrier screening came into wide practice, and 2003-2006. The number of live-born infants with cystic fibrosis dropped by about 50 percent from one four-year period to the next. Moreover, among the babies who were born, markedly fewer had two copies of the delta F508 gene mutation, associated with a severe form of CF.
The authors hypothesize that the gradual implementation of recommendations to offer pre-conception and prenatal screening to identify carriers of CF might have led to a decrease in the number of infants born with CF, particularly the type that causes the most severe disease.
"Our data cannot distinguish the reason for the reported decrease," notes Richard Parad, MD, MPH, a newborn medicine specialist at Children's Hospital Boston and Brigham and Women's Hospital, who co-authored the study with NENSP director Anne Comeau, PhD, and Jamie Hale of NENSP. "Carrier couples may have chosen not to conceive, or they may have resorted to donor egg or sperm or to pre-implantation genetic diagnosis, or they may have decided to terminate affected pregnancies."
The authors, who work closely with the clinician directors of the five Massachusetts CF Centers --at Children's Hospital Boston, Baystate Medical Center in Springfield, Massachusetts General Hospital, New England Medical Center and the University of Massachusetts Medical School--are confident that the decrease is real, not an aberration of the screening program and not a normal fluctuation.
Clinical researchers have understood that a major challenge of CF newborn screening is developing treatments to maintain the health of relatively asymptomatic newborns. "Our observations that fewer infants are being born with CF recently -- particularly fewer infants with a severe genotype -- provides an additional challenge to researchers developing new treatments or using population data for trend analyses," says Comeau, also an associate professor of pediatrics at the University of Massachusetts Medical School. "We should not fool ourselves into thinking that our treatments are working better than they are if the treatment may be tested on a population that was already bound to be more healthy."
CF affects all races, and is the most common autosomal recessively inherited disorder in Caucasians (about 1/3000 births). Fifty years ago, most children with CF died before they reached school age, but today, with early diagnosis and improved treatment, the median survival is 36 years.
The study was supported in part by the Health Resources and Services Administration of the U.S. Department of Health and Human Services.
Children's Hospital Boston is home to the world's largest research enterprise based at a pediatric medical center, where its discoveries have benefited both children and adults since 1869. More than 500 scientists, including eight members of the National Academy of Sciences, 11 members of the Institute of Medicine and 12 members of the Howard Hughes Medical Institute comprise Children's research community. Founded as a 20-bed hospital for children, Children's Hospital Boston today is a 397-bed comprehensive center for pediatric and adolescent health care grounded in the values of excellence in patient care and sensitivity to the complex needs and diversity of children and families. Children's also is the primary pediatric teaching affiliate of Harvard Medical School. For more information about the hospital and its research visit: www.childrenshospital.org/newsroom.
The University of Massachusetts Medical School, one of the fastest growing academic health centers in the country, has built a reputation as a world-class research institution, consistently producing noteworthy advances in clinical and basic research. The Medical School attracts more than $179 million in research funding annually, 80 percent of which comes from federal funding sources. The work of UMMS researcher Craig Mello, PhD, an investigator of the prestigious Howard Hughes Medical Institute (HHMI), and his colleague Andrew Fire, PhD, then of the Carnegie Institution of Washington, toward the discovery of RNA interference was awarded the 2006 Nobel Prize in Physiology or Medicine and has spawned a new and promising field of research, the global impact of which may prove astounding. UMMS is the academic partner of UMass Memorial Health Care, the largest health care provider in Central Massachusetts. For more information, visit www.umassmed.edu.
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