Noninvasive Blood Test Detects Down Syndrome

A new commercially available genetic blood test can identify Down Syndrome (DS) with a 99.1% accuracy rate by analyzing Trisomy 21 fetal DNA found in a pregnant woman's blood.

The MaterniT21 laboratory-developed test (LDT) analyzes the relative amount of chromosome 21 in circulating cell-free DNA from a maternal blood sample. Circulating Cell-Free Fetal Nucleic Acid (CCFF) DNA is purified from the plasma component of anti-coagulated maternal whole blood; it is then converted into a genomic DNA library for the determination of chromosome 21 representations, using SEQureDx, a proprietary, noninvasive technology. Rather than harvesting placental tissue cells or entering the uterus to sample the amniotic fluid, CCFF nucleic acid can be detected routinely at 12 weeks, allowing noninvasive fetal DNA tests in the 1st trimester.

To conduct the MaterniT21 test, a health provider takes a small sample of whole blood from a pregnant woman. The sample is shipped to the molecular diagnostics laboratory where a possible overabundance of chromosome 21 relative to the amount of other chromosomes can be measured. Physicians can expect to receive testing results in about 8-10 business days on average, at a cost (for insured patients) of no more than US$235. The MaterniT21 LDT test, a product of Sequenom (San Diego, CA, USA), is being offered by the Sequenom Center for Molecular Medicine (Sequenom CMM; Grand Rapids, MI, USA). The test has been approved by the US Food and Drug Administration (FDA).

“As we advance our role in developing and commercializing prenatal diagnostics, we believe this LDT will be a welcomed addition to the testing currently available to the prenatal and maternal care community,” said Harry Hixson, Jr., PhD, chairman, and CEO of Sequenom. “We believe that the MaterniT21 LDT will provide physicians and their patients with critical new information to help them make better informed decisions about the patients' healthcare and pregnancies.”

“Pregnant women can be safely assured that all we will be taking is just a blood sample,” added Professor Rossa Chiu, MD, PhD, of the Chinese University of Hong Kong, who helped develop the test. “The majority of cases would not need to go on to an invasive test such as amniocentesis.”

The source of the CCFF DNA is thought to be from placental cells, through the breakdown of fetal cells in circulation. Early studies have shown that around 3% to 6% of circulating fetal DNA is present in maternal plasma, while more recent studies indicate it may be as high as 10%. The core technology, which underlies the MaterniT21 test also has the capability to detect other aneuploidies, such as trisomy 18 and trisomy 13, according to preliminary studies.

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