When They Warn of Rare Disorders, These Prenatal Tests Are Usually Wrong

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 his "brother or sister" was in her belly. But a few weeks later, as she was driving her son home from school, her doctor's office called. A prenatal blood test indicated her fetus might be missing part of a chromosome, which could lead to serious ailments and mental illness. Sitting on the couch that evening with her husband, she cried as she explained they might be facing a decision on terminating the pregnancy. He sat quietly with the news. "How is this happening to me?" Ms. Geller, 32, recalled thinking. The next day, doctors used a long, painful needle to retrieve a small piece of her placenta. It was tested and showed the initial result was wrong. She now has a 6-month-old, Emmanuel, who shows no signs of the condition he screened positive for. Ms. 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. In just over a decade, the 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. The tests initially looked for Down syndrome and worked very well. But as manufacturers tried to outsell each other, they began offering additional screenings for increasingly rare conditions. The grave predictions made by those newer tests are usually wrong, an examination by The New York Times has found. That includes the screening that came back positive for Ms. 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 percent of the time. Nonetheless, on product brochures and test result sheets, companies describe the tests to pregnant women and their doctors as near certain. They advertise their findings as "reliable" and "highly accurate," offering "total confidence" and "peace of mind" for patients who want to know as much as possible. Some of the companies offer tests without publishing any data on how well they perform, or point to numbers for their best screenings while leaving out weaker ones. Others base their claims on studies in which only one or two pregnancies actually had the condition in question. These aren't the first Silicon Valley firms to try to build a business around blood tests. Years before the first prenatal testing company opened, another start-up, Theranos, made claims that it could run more than a thousand tests on a tiny blood sample, before it collapsed amid allegations of fraud. In contrast with Theranos, the science behind these companies' ability to test blood for common disorders is not in question. Experts say it has revolutionized Down syndrome screening, significantly reducing the need for riskier tests. 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.

Read more of this story at Slashdot.