A San Diego Company Develops a Test for Down’s
Tuesday, February 3, 2009
As women put off marriage and childbirth to later years, their risk of having babies with Down Syndrome goes up. A San Diego company is getting national attention for developing a blood test that seems to be a very accurate pre-natal test for Downs. KPBS Health reporter Tom Fudge has the story.
Longer life spans. The desire to get a college degree and start a career. There are many reasons why women, and men, are putting off reproduction to a later age. But the advantages of putting it off are weighed against the disadvantages that come with bearing kids in an older body.
As women age, they become more likely to have children with chromosome disorders, and the most common disorder causes Down Syndrome. Jason Chibuk is a genetic counselor at UCSD Medical center. He says as women get older their chance of having a baby with Downs increases dramatically.
Chibuk: A risk of Down Syndrome for a 25-year-old woman would be about one in a thousand. And for a 35-year-old woman would be one in 300. For a woman at 45 it's one in 22.
People with Down Syndrome commonly have broad, round faces and short stature. They typically have mild to moderate mental retardation, and they're at high risk for congenital heart disorders.
Getting a reliable prenatal test for Downs involves an invasive procedure called amniocentesis. Doing an amnio means inserting a needle into a woman's uterus to withdraw and test the amniotic fluid. The test is painful, it carries the risk of miscarriage, and it can't be done prior to the 16th week of pregnancy. Harry Stylli is CEO of a San Diego company called Sequenom. He says a test his company has developed could provide a better alternative.
Stylli: If our test continues performing the way it is, it's going to be a screening test that performs in the same ballpark as an invasive procedure.
Sequenom's prenatal test examines fetal gene markers in the expectant mother's blood. The company has, so far, examined 858 pregnant women and identified, among them, 28 cases of prenatal Downs. The test gave no false negatives. In other words, if the test told you didn't have a Downs baby, you really did not. And there was only one false positive.
Stylli: That's the way our test works. You're not dealing with risk factor anymore, right. You're absolutely going down to the genetic crux of the equation.
Sequenom hopes that its blood test will prove to be so accurate for Downs that it may someday replace the amnio. That means less pain for the mom and no test-related risk of miscarriage. And the test results would be available up to eight weeks earlier.
But independent clinical tests have yet to come, and doctors are cautious in talking about the Sequenom test. Chibuk, of UCSD, says he has purchased some Sequenom stock. Still , he says the one false positive makes him wary of comparing this blood test to an amnio.
Chibuk: Amniocenticus is 99.9 percent accurate. We're looking at the chromosomes from top to bottom to determine every chromosome whether there is extra or missing material.
Testing for abnormalities like Downs raises the question of what mothers will do with the information once it arrives. Very often the answer to that question is abortion. And that troubles some people who are family members of people with Downs. Brian Skotko is a physician at Children Hospital of Boston. He's the brother of a woman with Down Syndrome and he's a member of the board of the Down Syndrome Society.
He says he respects the right of women to choose abortion. But he says he wants expectant mothers to know the truth about Downs.
Skotko: Many people say having a child with Down syndrome will be disruptive to marriage. Yet there is new research that has come out that has shown that having a child with Down syndrome makes families less prone and parents less prone to having a divorce.
Skotko points out that his sister, who has Down Syndrome, lives every day to the fullest. And she has taught him how to enjoy the unique pleasures that nestle in small objects. Tom Fudge, KPBS News.