Illumina DNA Screen for Down Syndrome Found More Accurate

Illumina Inc.’s genetic screening for Down syndrome and Edwards syndrome provided a more accurate diagnosis than traditional techniques in a company-funded study.

The technology, called cell-free DNA testing, turned up significantly fewer false positives in a study of 1,914 women than standard serum screening, according to a paper released yesterday by the New England Journal of Medicine.

The study may support expansion of the testing to expectant mothers beyond only those considered at high risk for having babies with Down and Edwards syndromes, chromosomal conditions that lead to developmental issues. Traditional screening is often followed by more invasive procedures such as amniocentesis to confirm positive results; the more accurate cfDNA testing may significantly reduce those procedures, the researchers said.

“The major advantage of using cfDNA testing was the reduction in rates of false positive results,” the study authors, led by Diana W. Bianchi of Tufts Medical Center in Boston, wrote. The findings “suggest that cfDNA testing merits serious consideration as a primary screening method for fetal autosomal aneuploidy.”

Aneuploidy refers to conditions in which there are an abnormal number of chromosomes, the cause of Down and Edwards syndromes. The American Congress of Obstetricians and Gynecologists recommends offering screening tests to all pregnant women, according to the Mayo Clinic. They can involve ultrasounds and blood tests to measure protein and hormone levels.

Illumina rose less than 1 percent to close at $178.11 in New York. The company has more than tripled in the last 12 months.

Scanning Machines

The cfDNA test involved drawing a blood sample that was run through Illumina’s HiSeq 2000 machines. The San Diego-based company has been expanding its business in reproductive health in the last few years, acquiring Verinata Health Inc. for $350 million in February 2013 and BlueGnome Ltd. in 2012 for an undisclosed sum.

Three other companies in the U.S. provide cfDNA testing, Bianchi said in an e-mail. They are Sequenom Inc., Ariosa Diagnostics Inc. and Natera Inc.

The Illumina study today showed that cfDNA testing yielded a false positive rate of 0.3 percent for Down syndrome, versus 3.6 percent for the standard screening. For Edwards, the rates were 0.2 percent for cfDNA testing, compared with 0.6 percent for the standard technique.

Down syndrome, which occurs when a person has an extra copy of chromosome 21, affects about 400,000 Americans, according to the National Down Syndrome Society. About 6,000 babies in the U.S. are born with it each year. Edwards syndrome, caused by an extra chromosome 18, is less common and associated with more life-threatening medical complications, according to the Trisomy 18 Foundation.

High-Risk Patients

Currently, cfDNA testing is offered as an alternative to an invasive procedure in women at high risk for a major fetal chromosome abnormality, Bianchi said. While she doesn’t expect the study results to change practice immediately, they provide important information on how well the test works for pregnant women at low risk, she said.

At the University of California at San Francisco Medical Center, the cfDNA test is offered to women who will be at least 35 years old when their babies are delivered, or those found to be at increased risk for Down or Edwards syndromes with standard screening, according to its website. The center says the test isn’t standard of care and is considered investigational by some insurers, so may not be covered by all health plans.

Bianchi said insurers pay for some or all of the cost of the tests for most high-risk women. For others, the screening may cost $1,200 to $2,700 before discounts. The state of California has a discounted rate of about $400 in its prenatal test centers, Bianchi said.

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