Medical science and diagnostics have advanced significantly over the last few years, but they aren’t perfect. Unfortunately, some doctors and patients are making life-and-death decisions based on claims of accuracy that don’t match up to performance, especially when it comes to pre-natal testing for birth defects. Genetic tests that should be preliminary have been used to make final decisions, resulting in unnecessary abortions, the Boston Globe reported this weekend:

On that spring day in 2013, Dr. Jayme Sloan had bad news for Chapman, who was nearly three months pregnant. Her unborn child had tested positive for Edwards syndrome, a genetic condition associated with severe birth defects. If her baby — a boy, the screening test had shown — was born alive, he probably would not live long.

Sloan explained that the test — MaterniT21 PLUS — has a 99 percent detection rate. Though Sloan offered additional testing to confirm the result, a distraught Chapman said she wanted to terminate the pregnancy immediately.

What she — and the doctor — did not understand, Chapman’s medical records indicate, was that there was a good chance her screening result was wrong. There is, it turns out, a huge and crucial difference between a test that can detect a potential problem and one reliable enough to diagnose a life-threatening condition for certain. The screening test only does the first. …

Companies selling the most popular of these screens do not make it clear enough to patients and doctors that the results of their tests are not reliable enough to make a diagnosis.

California-based Sequenom Inc., for instance, promises on its web page that its MaterniT21 blood test provides “simple, clear results.” Only far down below does Sequenom disclose that “no test is perfect” and that theirs can produce erroneous results “in rare cases.”

Now, evidence is building that some women are terminating pregnancies based on the screening tests alone. A recent study by another California-based testing company, Natera Inc., which offers a screen called Panorama, found that 6.2 percent of women who received test results showing their fetus at high risk for a chromosomal condition terminated pregnancies without getting a diagnostic test such as an amniocentesis.

The story turned out happier for the Chapmans — but only after her doctor convinced her to stop the abortion:

Stanford University has three cases of unnecessary abortions prompted by faulty results on this test. One of those actually was told that a follow-up test showed that the baby had no such defect, but was convinced that the first test was so accurate it couldn’t possibly have been wrong.  But how exactly did doctors and patients get convinced so thoroughly that the tests are reliable? NECIR says it’s the sales pitch, because the FDA doesn’t actually vet the claims:

The screens are not subject to approval by the Food and Drug Administration. Because of a regulatory loophole, the companies operate free of agency oversight and the kind of independent analysis that would validate their accuracy claims. Doctors often get that information from salespeople, according to doctors themselves.

The errors go in the other direction, too. NECIR found women who had been assured that their babies were healthy when in fact they did have the genetic conditions for birth defects.

The blood tests have been designed to augment and perhaps eventually replace amniocentesis, which provides a highly accurate diagnosis but can create miscarriages on rare occasions. They screen for higher risk, and those testing positive are supposed to then have the amniocentesis to confirm. That would eliminate a significant number of unnecessary amnio tests and reduce the number of miscarriages as a result. Too many doctors and patients have treated the second test as optional, though, choosing instead to rely on a result that may not be accurate, from a test whose claimed accuracy may not withstand rigorous examination.

That is a tragedy for all involved, and one that should give all pause to consider what the sales pitch actually is for pre-natal testing such as this.

Update: I’ve changed the headline; I agree with some commenters that the word “unnecessary” is regrettable. “Mistaken” is a better choice. There really isn’t any such thing as a ‘necessary’ abortion, save for ectopic pregnancies that would result in death for the mother.