Family Matters

Could a Blood-Based Test Replace Amniocentesis?

A California company hopes to take the needles — and risk — out of prenatal genetic testing.

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A California company hopes to take the needles — and risk — out of prenatal genetic testing.

Each year, about 200,000 amniocentesis tests are performed, according to the Mayo Clinic, most during the first trimester of pregnancy to detect for genetic abnormalities such as Down syndrome. Based on the results, many parents make the difficult decision about whether or not to continue with the pregnancy. While safe, the procedure, which requires inserting a needle through the abdomen and removing small amounts of amniotic fluid containing fetal cells, is invasive and can result in miscarriage in 1 in 200 to 1 in 400 cases.

But researchers at Redwood City-based Verinata Health, which develops prenatal tests, report in the American Journal of Human Genetics that a blood test from an expectant mom may provide the same valuable information about potential birth defects that amniocentesis does, without the risk.

The scientists studied just 11 pregnant women who were carrying fetuses with chromosomal abnormalities. While that’s a small number of patients, the new test, which analyzed fetal DNA in the mother’s blood, was able to accurately detect the genetic changes. “There were no false positives and there were no false negatives so we say that the accuracy is greater than 99%,” says Richard Rava, chief scientific officer at Verinata Health.

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The test is based on a genetic sequencing technique that allows researchers to quickly scan specific regions of a person’s genome and compare it to a reference genome for any aberrations. Until now, such a detailed look at a fetus’ chromosomes has not been possible. Invasive procedures such as amniocentesis or chorionic villus sampling (CVS), which removes specks of placenta, could only provide karyotypes that exposed broad structural abnormalities in the shape of fetal chromosomes. In 2012, scientists proposed enhancing this information with more detailed genetic analysis of the baby’s genome, using microarray techniques that could identify places where DNA is duplicated or deleted. But this testing still required a sample of placental tissue.

“This is the latest in a string of developments,” says Jacob Kitzman, a graduate student at the University of Washington who headed the first sequencing of a fetal genome of the blood based test. “What’s impressive about this paper is that they were able to do the same thing as microarray, which is of course totally invasive. There’s zero risk from a blood draw and potentially this could be extended to expectant mothers who don’t have access to clinicians who can do more invasive tests.”

The approach used by the Verinata scientists does not provide the same comprehensive information as genome sequencing, but sequencing the entire genome isn’t always necessary when doctors know where the most common genetic mutations contributing to birth defects are found. Eventually, says Rava, relying upon a mom’s plasma to isolate and sequence fetal DNA could replace amniocentesis and CVS “as people get more and more confident with the information.”

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“This is right in between,” says Dr. Ronald Wapner, director of reproductive genetics at Columbia University Medical Center and lead author of the microarray study. “This paper proves that we can identify smaller and smaller alterations of the fetal genome by drawing blood from the mother. This is absolutely the appropriate next step.”

In March 2012, Verinata began selling a blood test that detects Down syndrome, along with a handful of other conditions that involve an extra chromosome. Rava says the company plans to expand that test, called verifi, to incorporate the additional chromosomal aberrations that the new study shows it can identify, which could take at least a year. “This paper demonstrates it’s technically feasible, but it’s not going to happen tomorrow,” he says.

Still, genome sequencing is becoming increasingly sophisticated and represents an important potential market in reproductive medicine. The results come as the biotech company Illumina, which focuses on commercial applications of sequencing technology, announced plans intends to acquire Verinata and PerkinElmer revealed it would partner with the company in marketing and distributing the verifi test. According to a press release from Illumina, the non-invasive prenatal testing market is expected to reach $600 million this year.

With the additional information that such testing can provide, however, come more challenges, says Wapner. “The easier it gets to get information about a fetus,” he says, “the more careful we have to be about how we use our technology.”

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