These prenatal tests are usually wrong when they warn of rare disorders



Between 2011 and 2013, a small, Silicon Valley-based biotechnology company, Sequenom, tripled in size. The key to its success: MaterniT21, a new prenatal screening test that has been remarkably successful in detecting Down’s syndrome.

Older screening tests took months and required multiple blood tests. This new test generated fewer false positives with a single blood test.

The test could also determine the sex of a fetus. It quickly became a hit. “People came in saying, ‘I want this sex test,’” recalls Dr. Anjali Kaimal, a maternal and fetal medicine specialist at Massachusetts General Hospital.

Competitors have started to run their own tests. Today, analysts’ estimates of the size of the market range from $ 600 million to billions of dollars, and the number of women taking these tests is expected to double by 2025.

As companies began to look for ways to differentiate their products, many decided to start screening for more and more rare disorders. All tests could take place on the same blood test, and doctors already order plenty of tests on short antenatal care visits, meaning some probably thought little about adding a few more.

For the testing company, however, the addition of microdeletions can double what an insurer pays – from an average of $ 695 for basic testing to $ 1,349 for the expanded panel, according to the data company. health Concert Genetics. (Patients whose insurance did not fully cover the tests describe very different amounts billed, ranging from a few hundred to thousands of dollars.)

But these conditions were so rare that there were few cases for testing to be found.

Take Natera, who performed 400,000 tests in 2020 for DiGeorge syndrome, a disorder associated with heart defects and intellectual disability.


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