Non-Invasive Prenatal Screening is not the Holy Grail of Prenatal Testing, and it’s wrong to call it that

Last week, I asked if Non-Invasive Prenatal Screening (NIPS) is the “Holy Grail” of prenatal testing? Here’s Part I of why it’s not and Part II will cover why it’s wrong to call it that.

My question was prompted by a blog post at the Huffington Post. The post’s author, Anne Drapkin Lyerly, is an obstetrician, a bioethicist, and served as the chair of the American Congress of Obstetricians & Gynecologists’ ethics committee from 2007-2009. She is also into her second pregnancy since turning 40 and praised NIPS as the “Holy Grail” of prenatal testing. Except, it’s not the Holy Grail.

Why is NIPS not the Holy Grail?

In addition to NIPS not being the cup from which Jesus drank at the Last Supper, it’s not even the thing that has long been sought after.

When the labs offering NIPS began promoting their testing, NIPS was originally referred to as “Non-Invasive Prenatal Diagnosis” or NIPD. NIPD is what remains the “Holy Grail” of prenatal testing: a non-invasive form of testing that can provide a diagnosis without the risk of miscarriage like the current diagnostic tests, usually amniocentesis or chorionic villus sampling. This is what is long sought after by practitioners and scientists: a way to diagnosis the pregnancy without risking ending it. NIPS doesn’t do this.

Instead, NIPS is a more accurate recalculation of the likelihood that a pregnancy is positive for Down syndrome–but NIPS is still a probability calculation. Those sorts of tests have existed since the 1980’s–indeed, every screening test is non-invasive, thereby posing no risk of miscarriage.

Those other sorts of screening tests, like AFP, the Quad test, and Nuchal Translucency, in the wake of NIPS, are now likened to Tarot Cards for their imprecision. But, as Lyerly acknowledges, NIPS still has false positives and false negatives and still an invasive test with the risk of miscarriage is needed even after a NIPS result to receive a true diagnosis. It is for this reason that the American College of Medical Genetics and Genomics (ACMG) made the point of referring to the new testing as Non-Invasive Prenatal Screening (NIPS), since the testing remains simply a screen, and not NIPD.

So, even in the sense of a long-sought after object, NIPS is not NIPD and, therefore, NIPS is not the “Holy Grail” of prenatal testing. Tomorrow’s post will cover why it was wrong for Lyerly to call NIPS the “Holy Grail.”