Silicon Valley has promised mothers a test to detect serious developmental problems in the DNA of the fetus with remarkable accuracy. But the grave predictions made by newer tests are usually wrong. From The New York Times.
After a year of fertility treatments, Yael Geller was thrilled when she found out she was pregnant in November 2020. Following a normal ultrasound she was confident enough to tell her 3-year-old son that his “brother or sister” was in her belly.
Geller had been misled by a wondrous promise that Silicon Valley has made to expectant mothers: that a few vials of their blood, drawn in the first trimester, can allow companies to detect serious developmental problems in the DNA of the fetus with remarkable accuracy. That includes the screening that came back positive for Geller, which looks for Prader-Willi syndrome, a condition that offers little chance of living independently as an adult. Studies have found its positive results are incorrect more than 90% of the time.Nonetheless, on product brochures and test-result sheets, companies describe the tests to pregnant women and their doctors as near certain.
However, the same technology — known as noninvasive prenatal testing, or NIPT — performs much worse when it looks for less-common conditions. Most are caused by small missing pieces of chromosomes called microdeletions. Others stem from missing or extra copies of entire chromosomes. They can have a wide range of symptoms, including intellectual disability, heart defects, a shortened life span or a high infant-mortality rate.
But there are hundreds of microdeletion syndromes, and the most expansive tests look for between five and seven, meaning women shouldn’t take a negative result as proof their baby doesn’t have a genetic disorder. For patients who are especially worried, obstetricians who study these screenings currently recommend other types of testing, which come with a small risk of miscarriage but are more reliable.
Alberto Gutierrez, former director of the FDA office that oversees many medical tests, reviewed marketing materials from three testing companies and described them as “problematic.”Patients who receive a positive result are supposed to pursue follow-up testing, which often requires a drawing of amniotic fluid or a sample of placental tissue.
In interviews, 14 patients who got false positives said the experience was agonizing. They recalled frantically researching conditions they had never heard of, followed by sleepless nights and days hiding their bulging bellies from friends. Eight said they never received any information about the possibility of a false positive, and five recalled that their doctor treated the test results as definitive.
Older screening tests took months and required multiple blood tests. This new one generated fewer false positives with a single blood draw. For the testing company, however, adding microdeletions can double what an insurer pays — from an average of $695 for the basic tests to $1,349 for the expanded panel, according to health data company Concert Genetics. Take Natera, which ran 400,000 tests in 2020 for DiGeorge syndrome.
Myriad Genetics’ prenatal test, Prequel, offers five microdeletion screenings, even though its study on the test includes just two confirmed cases of microdeletions. Genetic counselors who have dealt with false positives say some doctors may not understand how poorly the tests work. And even when caregivers do correctly interpret the information, patients may still be inclined to believe the confident-sounding results sheets.
Cloey and Colton Canida near their home in Tuolumne, Calif., Dec. 12, 2021. In just over a decade, fetal DNA tests have gone from laboratory experiments to an industry that serves more than a third of the pregnant women in America, luring major companies like Labcorp and Quest Diagnostics into the business, alongside many start-ups.
Three experts reviewed marketing materials and results sheets for The Times and identified obvious reasons a patient would be confused.
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