A week ago, I attended the American College of Obstetricians & Gynecologists’ (ACOG) Annual Clinical Meeting in Chicago. It was a quick trip, where I met with each of the non-invasive prenatal screening (NIPS) laboratories before getting back on the road to return home. Something I saw there prompted the title of this post.
How accurate are the new blood tests for Down syndrome?
This past weekend was the Kentucky Derby. So, odds have been at the forefront for all us Louisvillians: which horse to bet on, what odds are they going off at, and can we couple them with two or three others for an exotic bet: an exacta, trifecta, or superfecta?
This thinking about odds should also be kept in mind for every woman accepting non-invasive prenatal screening. Be it Sequenom’s MaterniT21, Ariosa’s Harmony, Illumnia/Verinata’s verifi, or Natera’s Panorama, a very critical point needs to be appreciated:
None of the new blood tests provide a definite answer.
None. Of. Them.
No matter how the results are reported, you should understand that if you are pregnant, and you get a non-invasive prenatal test result, it is never positive or negative.
NIPS tests are screening tests. They are a recalculation of the probability that your child may–emphasis on MAY–have Down syndrome (or one of the other conditions they test for). Every one of these tests has false positives and false negatives.
What are patients being told?
But note what Sequenom highlights on its booth for its MaterniT21 test:
Clear, direct results
+ Positive or negative results
- No risk score!
Sequenom highlights this as though it’s a good thing. In fact, it’s against ACOG’s own professional guidelines.
When ACOG changed the standard to offering prenatal testing for Down syndrome to all women (versus only those over the age of 35), it emphasized that results should never be relayed as a “positive” or “negative.” Instead, results should be presented as a probability calculation (or “risk score”).
But, here is Sequenom, the market-leading NIPS company, highlighting that it reports its results contrary to these professional recommendations, as though it is a selling point for its testing.
Invasive testing is the only option for a definitive answer.
ACOG’s statement on NIPS recommends that patients should be counseled that confirmation is needed with diagnostic testing because no NIPS test is a true positive or true negative. But, what is a mom to think when her test result is reported by the testing lab as a “positive” and not a probability ratio?
Sequenom is not the only lab to suggest its test results are more accurate than they actually are. But if you are receiving these test results, you need to understand that none–NONE–of the new blood tests provide true positives or true negatives. You can only gain that certainty through invasive testing.
NIPS tests remain just screening tests. They are never truly positive or truly negative. Get confirmation through invasive testing if knowing for sure is what you thought you were buying with a NIPS test.