When They Warn of Rare Disorders, These Prenatal Tests Are Usually Wrong
Prenatal blood tests have mastered the science of detecting Down syndrome in unborn babies, but an investigation by the New York Times finds that newer screens looking for rarer disorders are failing expectant mothers. As more companies enter the space and try to compete, they are marketing their technologies as accurate and reliable — even though test performance declines the more uncommon the condition it targets. Microdeletion screens, which look for chromosome anomolies that cause developmental problems in the fetus, are wrong roughly 85% of the time that they return positive results, the Times calculated, using the top five tests as its basis. Among them, screens for Prader-Willi and Angelman syndromes were most inaccurate, with a false-positive rate of 93%. Not far behind were tests for Wolf-Hirschhorn syndrome, at 86% inaccurate; 1p36 deletion, at 84%; DiGeorge syndrome, at 81%; and Cri-du-chat syndrome, at 80%. Given the large window for potentially inaccurate findings, some obstetricians suggest that parents with real concerns might consider more reliable forms of testing, although these generally have a slight risk of miscarriage.
Read more on The New York Times.