Down Syndrome Tests Enter New DNA Era

down syndromeA new study by Tuft’s Medical doctors in Boston suggests the testing for diseases like Down Syndrome is entering a new era dominated by DNA tests. The research hopes to lower the number of traditional diagnostic procedures, which are much more invasive.

Researchers say the DNA testing method leads to results faster than traditional methods and that those results are more accurate. If the claims are true it will allow mothers to decide on the fate of the pregnancy sooner, leaving more time to contemplate abortion or adoption.

Traditional procedures for Down Syndrome testing begin with ultrasounds and blood tests. Though, these tests only uncover the possibility of a problem. The steps which ultimately determine real trouble have the risk of miscarriage.  One procedure is an amniocentesis, a process which includes the insertion of a needle into the amniotic sac. The alternative called, chorionic villus sampling, samples a piece of placenta taken from the mother.

Dr. Diana Bianchi, the study leader from Tufts, remarked on the safety of the DNA testing. ‘‘It offers…a safe and accurate alternative,” she said. Numerous companies offer the DNA testing, which can be performed as early as nine weeks into the pregnancy. The hope is that more women will opt for this test first, lowering the number of risky invasive procedures.

The DNA test takes a sample of the blood from the mother and tests the DNA coming off the placenta. This DNA sequence is then compared to the normal chromosome counts for its respective stage of pregnancy. The tests are now targeted at high-risk pregnancies. 35-year-old women or older, women with unusual blood tests and women with previous high-risk pregnancies are all recommended the DNA test.

The new study for the DNA test, which searches for signs of Down Syndrome and related diseases, is hoping to enter an era where the procedure will be used in the general public. The findings, published in the New England Journal of Medicine, said the false alarm rate for test results was significantly lower than than of standard procedures.

The false alarm rate for the DNA test was .3% while standard procedures remain at 3.6%. The same trend was found in other chromosomal abnormalities like Edwards and Patau syndromes.

If implemented, this could bring down the number of women suggested for invasive procedures. When unusual results are found early in pregnancy, a next step has to be taken if the mother wants more information. Here is where the DNA testing hopes to step in, replacing methods like amniocentesis.

Criticism arose for the findings of the study. Dr. Nancy Rose, a Utah professor who heads the genetics committee of the College of Obstetricians said the study was “encouraging,” but further testing would need to be done. Nearly one third of the women who participated in the study were in the third trimester of their pregnancy.

Doctors would like to see more supporting evidence in the early stages of pregnancy. The cost of the DNA testing is also a problem. The cost for the DNA test is between $1,200 to $2,700 while current tests run from $200 to $300.

For now, early pregnancy will depend on traditional tests, but the doctors of this study hope one day all women will be able to use the DNA testing to screen for diseases like Down Syndrome.

By Erin P. Friar


Boston Globe

Science World Report


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