DNA Blood Test Could End Risky Tests For Down's Syndrome

An accurate new DNA blood test could almost eliminate the need for risky invasive tests for Down's syndrome, according to a research published.

Down's syndrome, a major developmental disorder also called trisomy 21, occurs in around one in every 800 live births.

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Down Syndrome is a congenital disorder among children commonly born to older mothers. The condition is also known as ‘Up syndrome’ because of the cheerful persona of the Down children.

Pre-natal diagnosis mainly entails sampling fluid, drawn by a needle, from the amniotic sac enveloping the foetus. Another technique is called chorionic villus sampling, and entails taking a sample of placenta.

Both techniques, though, carry a roughly one-percent risk of miscarriage, which is why they are reserved for older mothers-to-be and other women deemed at risk.

Researchers led by Dennis Lo, a professor at the Chinese University of Hong Kong, carried out the first large-scale investigation into new DNA technology which sequences telltale foetal molecules in maternal blood.

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The test was carried out among 753 women who were all in the high-risk category.

Eighty-six of them were found to be carrying a foetus with Down's. The test detected this with 96.6 percent accuracy and did not deliver any "false negatives," meaning that it wrongly said a woman did not have a Down's foetus.

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"The sequencing test could be used to rule out trisomy 21 among high-risk pregnancies before proceeding to invasive diagnostic testing," says the study, published online by the British Medical Journal (BMJ).

Source-AFP

Amniocentesis
Amniocentesis is a procedure done after 15th week of pregnancy to obtain samples of the amniotic fluid to test for genetic disorders. A simple animation depicting the procedure.