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A First for Genetic Testing

Obstetrics: New prenatal guidelines aim to detect cystic fibrosis. The change offers hope for better treatment but also raises tough ethical issues.


A recommendation by influential physicians' groups that expectant parents receive counseling about genetic testing for cystic fibrosis--an incurable disease that's often fatal by early adulthood--brings the era of genetic testing a step closer to many families.

The new guidelines mean that more parents will learn early in a pregnancy that a woman is at risk of bearing a child with cystic fibrosis. That knowledge could lead to earlier and possibly more effective treatments for newborns with the disease. But the genetic tests also raise difficult ethical issues for doctors and expectant parents, who in some cases might decide to terminate a high-risk pregnancy after receiving unfavorable test results, experts acknowledge.

The recommendation was made last month by two medical organizations, the American College of Obstetricians and Gynecologists and the American College of Medical Genetics, after years of debate and study.

The guidelines state that doctors should advise couples about a test, known as carrier screening, to determine if an individual carries the gene that causes CF. This counseling could be offered at the time a woman sees a doctor for pregnancy planning or during the first office visit after pregnancy.

If the prospective parents opted for testing, the woman would have a blood or saliva test to identify the defective gene. If she were found to carry the gene, the father could then also undergo testing to determine his carrier status. Both parents must carry the gene for the baby to have cystic fibrosis, and in such cases the child has a 25% chance of having the disease. Some parents might decide to terminate the pregnancy if subsequent testing of the fetus shows it will have cystic fibrosis.

The couple's decision, however, could be complicated by several factors. The tests, for example, cannot determine how serious the disease will be; there are mild to severe forms of cystic fibrosis.

And no test can predict how future medical advances may improve treatments for the disease. Scientists are hopeful that better medications and the potential for gene therapy treatments will improve life expectancies for cystic fibrosis patients.

One reason for genetic testing would be to consider an abortion if a child carried the gene, said Michael Watson, executive director of the American College of Medical Genetics. "But there is some question about using the test for that reason. ... Kids with CF used to die much younger than they do now." On the other hand, he said, some couples may consider any form of the disease too severe to continue the pregnancy.

There is no cure for cystic fibrosis, although treatment for its symptoms has improved dramatically in the last decade. The average life expectancy for those with the disease is about age 30. Most people with CF require close medical supervision and often need daily treatments to clear mucus from their lungs.

Doctors who helped draw up the new guidelines emphasized that they are not recommending testing for parents but simply that potential parents be informed that the test is available and why, said Dr. Michael T. Mennuti, a Philadelphia obstetrician. "The decision is their decision," he said. "It's a complex and personal choice."

That sentiment was echoed by the Cystic Fibrosis Foundation, the nation's leading advocacy group for the disease. A foundation official was reluctant to comment on the physician groups' recommendations. "We believe testing is a very personal decision," says Suzanne Pattee, vice president for public policy and patient affairs. "We don't believe our organization should impose its views on anyone."

Cystic fibrosis is the most common recessive genetic disorder in Caucasians, affecting about one in every 3,300 babies born. It is less common in other ethnic groups. Individuals with CF have a defect in the chloride transport mechanism in the cells. This results in the thick mucus in the lungs and pancreas that are the disease's major characteristics.

The gene responsible for CF was identified in 1989, and carrier screening tests were developed a short time later. The test, however, was usually recommended only for people known to be at high risk for having children with CF, such as people with relatives who have the disease.

It is not uncommon for certain groups to be offered screening tests for a specific gene defect. Ashkenazi Jews, for example, often choose to undergo screening for the gene that causes Tay-Sachs disease in newborns. But the CF carrier screening recommendation is the first to target a broad population, Watson said.

The recommendation comes four years after the National Institutes of Health, the federal government's medical branch, urged that prospective parents be offered genetic testing for cystic fibrosis. It has taken four years to implement the program because of the complexities involved, Watson said.

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