Blood-Based Prenatal Genetic Tests Greeted with Skepticism

By Joe Elia

Newer prenatal tests for genetic abnormalities, touted by some as alternatives to amniocentesis, are getting wider use and presenting familiar problems.

Four companies have entered the market, selling products that range in price from $800 to almost $3000, according to a report in the Wall Street Journal. The tests (or "screenings," as one national genetics group would like to call them) use fetal DNA from the mother's blood rather than relying on amniocentesis.

The tests' accuracy has been established in clinical trials, but in real-world practice "the numbers usually tend to be not quite as good," according to one expert. False-positives could lead to unneeded abortions, and false-negatives may become apparent only much later in the pregnancy.

"Positive results should be confirmed with invasive testing," according to one company official. Another says, "it is important to understand [the new tests] don't replace invasive tests yet."