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Are We Ready to Embrace Prenatal Blood Tests?

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It's a tantalizing technology for a pregnant woman: a few weeks after a missed period, before anyone else knows she's pregnant, she goes to a lab, has her blood drawn and learns whether her fetus is a boy or a girl, has Down syndrome or another genetic abnormality, and even learns about its blood type.

In the field of prenatal diagnosis this has become a holy grail of sorts, with researchers chasing a reliable test, and diagnostics companies lapping at their heels to bring the tests to market and reap the financial rewards.

So when over 650 news reports covered the August 10th publication in the Journal of the American Medical Association by Dr. Diana Bianchi and colleagues, one might have thought the research team was describing a novel breakthrough. But they weren't: Instead, they meticulously cobbled together hundreds of small studies by other researchers and demonstrated convincingly that when performed appropriately, beginning three weeks after she misses her period, a woman can count on the results from a blood test to tell her whether she will have a boy or a girl.

Why all the hubbub about an article summarizing old research?

I think that the reason is that after fits and starts, delays and controversies, a world-renowned researcher has published an article in a world-renowned medical journal giving this technology two thumbs up. Dr. Bianchi leads the Mother Infant Research Institute (MIRI) at Tufts Medical Center in Boston, and is a leading investigator in this field. (Full disclosure: I too am a MIRI researcher at Tufts.)

"Not only did the analysis demonstrate a surprisingly consistent performance over a 14 year period, it showed that some European countries were already using this test clinically to manage pregnancies at risk for certain genetic conditions," Bianchi told me.

My prediction is that this publication will be a catalyst for the acceptance of future non-invasive prenatal diagnosis tests -- from Down syndrome to cystic fibrosis and a host of other tests that are still under development.

To understand why this is a big deal, a bit of background is in order:

Information about the fetus' gender can be critically important: Some genetic abnormalities of the X-chromosome -- like hemophilia or Duchenne muscular dystrophy -- typically affect only boys, and another condition that causes ambiguous genitalia among other problems, called Congenital Adrenal Hyperplasia, can be successfully treated in-utero if the gender is known.

Also, parents like to know what gender to expect. (This can lead to sticky ethical issues when the information is used for gender selection, but that topic has been well covered elsewhere so I'll leave it alone.)

The gender test, along with the test for Down syndrome and other chromosomal problems, offers the potential to get a diagnosis early in pregnancy without the need for an invasive procedure -- a chorionic villus sampling or an amniocentesis -- that can cause miscarriage.

Since 1997, when scientists first reported that they could isolate fetal nucleic acids -- the stuff our genes are made from -- in maternal blood, the chase has been on for reliable fetal diagnostic tests.

But 14 years later, only one test has made it into the mainstream -- the non-invasive test for fetal blood Rh status, launched by Sequenom last year. For the 12 percent of pregnant women in the United States who have Rh-negative blood type -- and particularly for the small fraction of these women who make antibodies that can attack their fetus' blood if it's Rh-positive -- this test is a godsend.

The gender test has remained in the periphery, available only online through largely unregulated companies. One company went bankrupt after being sued by a host of women who painted their nurseroes the wrong color. Regulations that would bring the test into the mainstream have not been written, and as a consequence, insurance companies do not cover the approximately $250 cost of the test.

Worse yet is the saga surrounding the test for Down syndrome, which was due to be released by Sequenom until it turned out the company had cooked their data. The fraud delayed the test's release by years.

Understandably, after delays, fraud and internet sideshows, clinicians, scientists -- and even patients -- are a little jaded.

To see an article in a top journal that reads like an endorsement of the technology will do a lot to reinvigorate non-invasive prenatal diagnosis -- perhaps the most important advance in that field in decades.

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