The following comes from an April 3 story in the Wall Street Journal.

New prenatal blood tests for genetic abnormalities such as Down syndrome are reshaping care for expectant mothers, but their rapid rollout has raised fears that poorly understood results could lead to confusion among patients and doctors managing high-risk pregnancies.

Four companies, including Sequenom Inc. and a unit of gene-sequencing firm Illumina Inc., are vying for the new market for the tests, which examine traces of fetal DNA in the mother’s bloodstream. The market has grown rapidly since the tests were first introduced in late 2011—with Sequenom alone topping 61,000 tests in 2012. The industry expects that at current rates it will run hundreds of thousands of tests this year, and many doctors believe they could fast become the standard of care for pregnant women.

At the same time, case reports of inaccurate results—though rare—are turning up more frequently than expected, medical specialists say. They worry that in the worst-case scenario, inaccurate test results could contribute to the abortion of healthy babies.

Members of the American College of Medical Genetics and Genomics question whether the products should be called “tests” at all. The group plans to release a statement renaming them “screenings,” to indicate they predict risk rather than give definitive results, according to Anthony Gregg, a board member at the college and a specialist in treating high-risk pregnancies.

As physicians begin deploying the tests more routinely, experts worry they are being used in lieu of more invasive—but more definitive—diagnostic measures such as amniocentesis, in which a needle as long as 6 inches is inserted into the womb to extract fluid. That test carries a slight risk—generally estimated at well below 1%—of inducing miscarriage. Some clinics have promoted the new tests as a safer alternative.

Test makers and experts say positive results in a blood test should be confirmed with invasive procedures. Negative results may help rule out the need for such procedures.

But there is a risk that aggressive marketing based on test performance from the early clinical trials could confuse physicians and patients with complex information, said Girish Putcha, a practicing molecular-genetics pathologist and former laboratory director for Ariosa Diagnostics Inc., one of the test makers.

In translating clinical trials—focused on high-risk women and carried out in controlled environments—”to the actual practice of medicine, the numbers usually tend to be not quite as good,” Dr. Putcha said, speaking broadly about the industry. “The question is, how not-quite-as-good?”

Test race:

  • Ultrasound screening: Doctors can predict Down syndrome by seeing a thicker-than-normal layer of fluid behind the neck of a fetus. Up to 70% accurate
  • Serum tests: Combining ultrasound with blood tests seeking certain proteins can improve detection rates. Alone, the blood tests are less precise. Up to 87% accurate
  • Noninvasive prenatal testing:Fetal DNA in a mother’s blood is scanned for genetic signs of Down syndrome. More than 99% accurate
  • Amniocentesis: Using a needle, doctors extract amniotic fluid from the uterus for testing. Nearly 100% accurate….

“Women and physicians will do almost anything to reduce their need for invasive testing. That is why it is taking off,” said Lee Shulman, chief of clinical genetics for Northwestern Medicine’s obstetrics unit in Chicago. But while the tests are “a profound improvement over the tarot cards we used to use” to screen for risk, they don’t replace amniocentesis, he said.

In one case, Dr. Shulman, who consults for Sequenom and Natera Inc., another test maker, said one patient who had received a positive Sequenom test result for a chromosomal abnormality arrived at his clinic seeking to terminate her pregnancy, but amniocentesis showed the fetus was normal….

The tests have quickly changed care. At the Cleveland Clinic, doctors perform 50% fewer invasive procedures, thanks to the testing advances, said Jeff Chapa, section head of obstetrics and maternal-fetal medicine.

“This is my first child, and I’m 43. I’m not sure I want to risk this miracle that I have,” said Jennifer Turcotte of Redwood, Calif., who is 14 weeks into her pregnancy and at risk of abnormalities because of her age. After learning about the miscarriage rates associated with invasive testing, she opted to receive one of the new tests at Lucile Packard Children’s Hospital. The results tentatively ruled out problems. It “took a lot of that stress and anxiety away,” she said.

In addition to reducing the risks of complications, the tests appeal to women because they can be performed earlier in a pregnancy—beginning at about 10 weeks, offering a head start on potentially difficult decisions.

But false-positive results raise the specter that women could choose to terminate healthy pregnancies if they don’t receive appropriate follow-up care. False-negative results, which are rarer, also present a quandary for women and doctors who may not find out until much later that a fetus has an abnormality.

Some medical practices advertise the tests as a way to avoid amniocentesis. New Jersey Perinatal Associates in Livingston, N.J., describes Sequenom’s MaterniT21 test in a promotional page of its website as “an alternative to traditional” methods, and notes that unlike invasive tests, it “is a simple blood test that is noninvasive to you and your baby.”

“All patients want to hear that you don’t need to have something invasive,” said Laura Limone, genetic-counseling supervisor at the perinatal group and a member of Sequenom’s speakers bureau. “Those who understand the technology find it very promising, but we also know it isn’t perfect yet,” and patients with positive results are advised to undergo follow-up invasive testing, she said.

In one case published online by the American Journal of Obstetrics & Gynecology, a positive result from one of the new tests—together with preliminary results from another less-precise invasive measure—prompted a patient to terminate her pregnancy without undergoing a confirmatory amniocentesis. Testing of tissue from the aborted fetus showed the pregnancy was normal, the report said….

At least one case of a false-negative report also raised questions. Verinata, Illumina’s testing unit, incorrectly cleared a New York woman’s fetus of Down syndrome, according to the case report presented at a medical society meeting last month. Further testing prompted by unusual ultrasound readings later determined that the fetus did, in fact, have Down syndrome, and the patient opted to terminate the pregnancy.

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