A long anticipated joint statement regarding noninvasive prenatal testing (NIPT) from The American College of Obstetricians and Gynecologists (ACOG) and SMFM is now available, Committee Opinion #640 Cell-free DNA Screening for Fetal Aneuploidy. It is thorough and provides the guidance that many healthcare providers and organizations have been waiting for as they navigate how to responsibly implement this technology into practice. Here are the highlights: …
First off, let me introduce myself. My name is Carla, and I am an integral part of the Genetic Support Foundation (GSF) Team. Well, at least the idea of “me” has become near and dear to the folks at GSF. I am actually the star of their new video on noninvasive prenatal testing (NIPT). But, I am really much more than that; I represent women who are pregnant and trying to sort through all of the prenatal testing options out there. How is one supposed to make these decisions? Pregnancy is hard enough with all of these hormones and food cravings. I have been driving through the Taco Bell drive-through every. Single. Day. They know me by name and my order by heart; I digress.
So, since I am going to be 35 at delivery, one of the tests my doctor offered me is noninvasive prenatal testing (NIPT). You may have heard this test called by other names such as NIPS, cell free DNA testing or brand names such as, Panorama, MaterniT21, Harmony, Verifi, informaSeq, etc. I guess this is a newer prenatal screening test, as I didn’t know about it during my last pregnancy in 2010 (apparently it came out in 2011). Last time around I decided not to have any screening because I was 30 and I wasn’t really worried. But this time things feel different, and everyone keeps talking about my age! What’s up with 35?
Anyway, here I am trying to weigh all of my options…should I have NIPT or should I consider going straight for more definitive answers and have a test like CVS or amniocentesis? Or, am I ok skipping all of them and just waiting until the baby is born to know if he/she has a genetic condition?
My partner and I just met with a genetic counselor, which was super helpful. The genetic counselor was able to help us by not only explaining all of our testing options, but providing us with some questions to think about to help us decide what testing, if any, was right for us given our beliefs, values, personality and needs. Genetic counselors don’t tell you what to do, they simply give you the information necessary to help you make a decision that is right for you!
Another thing that was helpful to me was being a part of the NIPT informational video produced by GSF that I mentioned earlier. You should really check it out! This video explains how NIPT works, what conditions it can screen for, what results can and cannot tell you and how to decide if this test is right for you.
I’m still in the process of figuring out my prenatal testing plans, but I know I am on the right track and the information at www.geneticsupportfoundation.org is equipping me to make a decision that is right for me!
On behalf of the GSF Team, thanks for reading Our 2 Strands!
Let’s stay in touch,
P.S. Send a comment to GSF through our Get Connected page if you can guess why my name is Carla! First person to guess correctly (who isn’t related to someone on staff) will win an official Genetic Support Foundation T-shirt!
Noninvasive Prenatal Testing (NIPT) screens for a handful of genetic conditions. The detection rate of NIPT is high for many of these conditions, especially for Down syndrome. Many labs boast that their NIPT is “greater than 99% accurate”. So what does “>99% accurate” really mean? Let’s start first with what it does not mean:
A positive NIPT result rarely ever means that there is a greater than 99% chance that the baby has a genetic condition!
In fact, if your NIPT result is positive, the chance your baby actually has the condition is usually far less than 99%. So how do we answer the question: what is the chance my positive result is a true positive result? For this we need to know the Positive Predictive Value (PPV). Learn more about PPV here.
Are the claims of 99% accuracy false advertising? Actually, they are not false at all, but it is important to keep the magnitude of these claims in perspective. Accuracy refers to the proportion of all test results that are correct, both positive and negative results. Since NIPT screens for relatively rare conditions, most results will be negative indicating a low chance for the conditions screened and indeed they will be true negatives. The rarity of the conditions screened makes achieving 99% accuracy quite attainable!
Interestingly, if one were to write “negative” on a piece of paper and give it as the result to every single patient, it would be a “99% accurate” test result when testing for a condition that is present in less than 1 out of 100 people.
In this case of just calling all results negative, 99% of women would have true negative results: The given test predicted that their baby was unaffected and in fact the baby is unaffected. Of course, unlike NIPT, which has a high detection rate, a method that assigns a “negative” result to every patient across the board is not at all precise and the detection rate of such a screen is a big fat zero. This example is used merely to illustrate the point that claims of >99% accuracy aren’t necessarily anything to be impressed by.
What is more important is the sensitivity (detection rate) and specificity (false positive rate) so that personalized predictive values can be calculated for each individual. These are the numbers that will allow an individual to determine the chances that their negative result is a true negative (negative predictive value) or that their positive result is a true positive (positive predictive value).
Because most women start off with a very small chance to have a baby with any of the conditions for which NIPT screens, the negative predictive value for NIPT is high, usually >99%: most women will have negative results indicating that the chance of a having a baby with any of the screened for conditions is low and most of these women will have true negative results since the conditions are generally rare. On the other hand, the likelihood that a positive NIPT result is a true positive result (positive predictive value) is often to be far less than the coveted 99%. For more information about NIPT, click here.
Nearly four years into the use of this new prenatal screening test, and the medical community is still trying to figure out what to call it. When Sequenom first launched the MaterniT21 screen for Down syndrome in 2011 this type of testing was labeled “Noninvasive Prenatal Diagnosis” or NIPD. This was coupled with a tremendous amount of hype that NIPD would replace the need for invasive diagnostic testing such as amniocentesis. It didn’t take too long before we realized that to include “diagnosis” in the test name was overstated, so the name was soon dialed back to “Noninvasive Prenatal Testing” (NIPT). But many, most notably the American College of Medical Genetics and Genomics (ACMG), suggested that calling this “testing” did not go far enough to highlight the limitations and proposed that this technology be referred to as “Noninvasive Prenatal Screening” (NIPS). The Prenatal Information Research Consortium recently has used the term, Noninvasive Prenatal Genetic Screening (NIPGS).
Many in the field have discomfort with any name that includes “noninvasive” as the word, in and of itself, implies that this test should be compared to invasive tests and not to other screening tests. Aren’t all previously available aneuploidy screening tests (first trimester screening, sequential screening, Quad screen, etc.) noninvasive after all?
Recent publications from the Society of Maternal Fetal Medicine (SMFM) and the American College of Obstetricians and Gynecologists (ACOG) refer to the test as something along the lines of, “aneuploidy screening with cell free DNA (cfDNA)”. This solves the “noninvasive” issue however all stated it is quite a mouth full. Additionally, it will be technically problematic as the list of screened conditions moves beyond aneuploidy. And to call it only “cfDNA screening” may be confusing as new applications beyond prenatal screening are developed for cfDNA, such as the emerging ‘liquid biopsy‘ for cancer.
The National Society of Genetic Counselors (NSGC) Prenatal Special Interest Group recently surveyed members regarding what they call this test. This survey found that NIPT was the front runner with 45% of the vote as compared to 31% using NIPS and 23% using cfDNA. Another question to consider is: what name are patients most familiar with? Our survey of patient forums reveals that many patients seem to know these tests by specific brand names, which may be attributed to the successful direct to consumer marketing campaigns of the testing companies which prompt patients to “ask your doctor for the Harmony/verifi/Panorama/MaterniT21 Plus test by name!” Anecdotally, many patients have come to know this test as simply, “that new gender test”.
Developing educational resources regarding prenatal tests is a high priority for Genetic Support Foundation. As we developed content for our website and a patient education video about the NIPT/NIPS/NIPGS/cfDNA test, we spent a lot of time debating what to call this technology. We ultimately landed on NIPT for two reasons:
In the past, I have been a strong advocate for the term noninvasive prenatal screening. I would always pronounce each individual letter N-I-P-S. Recently at a genetics conference, I heard someone call it “Nips” and my jaw dropped. How had I failed to make the connection between the NIPS acronym and a slang term for a body part? The connection was set when I searched for #NIPS on twitter. Needless to say, I didn’t find much about prenatal screening – but instead found a lot of people talking about cold weather, underwear (or lack thereof), and photos of non G-rated fashion! A crash course in the importance of word choice for social media to be sure!
So for now, GSF has made the decision to stick to NIPT, but we will stay flexible and see where this interesting ride takes us. Who knows, maybe some day when we type in NIPS in a twitter search something G-rated involving prenatal screening will be near the top of the list.
While we have you here, take a moment to check out our video on NIPT, which began our inner turmoil on what to call this test. We believe this video provides a good overview of the testing – what it can and cannot tell you and also what women should think about prior to deciding whether or not to undergo NIPT, NIPS, NIPGS, cfDNA testing or whatever the heck you call it :-).
P.S. After watching the NIPT video please complete the post-viewing survey!