CF screen: still too soon.

CF screen: Still too soon

Both the medical community and the general public rejoiced in August after learning that researchers had identified the gene responsible for most cases of cystic fibrosis (CF) -- the most common lethal genetic disease of U.S. children. Before long, they were assured, the discovery would lead to genetic tests capable of identifying prospective parents harboring the gene and facilitating prenatal testing for the defect.

Sure enough, companies have begun advertising such tests -- but their initial announcements may have overstated the tests' value, says Michael M. Kaback, a board member with the American Society of Human Genetics (ASHG). "It would be premature to go out and screen [widely] with a test that's this imperfect," he says. Kaback, a pediatrician at the University of California, San Diego, notes the test misses the 30 percent of cystic fibrosis gene carriers whose defect differs from the one so far identified, risking false reassurance.

Kaback told reporters at the ASHG annual meeting in Baltimore this week that Collaborative Research, a Bedford, Mass.-based biotechnology company, has sent letters to doctors suggesting it might be appropriate to begin offering the test widely. Instead, Kaback says, the test should be reserved mostly for prospective parents who know they have a close relative carrying the gene. Linda Pine, a spokeswoman for Collaborative Research, told SCIENCE NEWS that the letter is now unavailable and that the company is offering to perform the test but not specifically recommending it.

Francis S. Collins of the University of Michigan in Ann Arbor, who helped discover the CF gene with Lap-Chee Tsui of the University of Toronto Hospital for Sick Children, says two obstetricians have already asked him whether they'd be legally liable for not suggesting their pregnant patients get tested. Within two years, Tsui says, he expects to see a test capable of detecting 95 percent of CF carriers.