Prenatal genetic testing can raise as many questions as it answers

Welcome to Small Humans, an ongoing series at Mashable that looks at how to take care of – and deal with – the kids in your life. Because Dr. Spock is nice and all, but it’s 2019 and we have the entire internet to contend with.

In 2016, I took a genetic carrier screening test and learned I was a carrier for Gaucher’s, a rare metabolic disorder more common in Ashkenazi Jews that can lead to serious health complications. The test results after I logged in on the website said Positive: Carrier, with risk of 1 in 63 that I would pass this on to my child.

This number did what it was supposed to: It got my partner running to get tested, and it scared me. But it came with a big asterisk. The fine print – only accessible when you actually open the report – said this number was based on “a hypothetical pairing with a partner of the same ethnic group.” While I’m of Ashkenazi descent, my partner is not, and the carrier frequency for Gaucher’s outside the Ashkenazi population is less than one percent. He ended up testing negative for Gaucher’s, and positive for a few other conditions I did not carry and our doctor had never heard of. The panel we took had over 100 diseases on it, so it was not surprising we hit something.

Carrier testing, which determines if parents are carriers for diseases they don’t themselves have but could pass on to offspring, can be lifesaving. Many of these conditions are autosomal recessive, so if both parents are carriers there is a 25% chance that their children would have it. This knowledge can empower parents to make decisions about how to best plan their families.

Carrier testing used to be offered only to certain higher-risk ethnic groups, such as Ashkenzani Jews, and for diseases such as Tay-Sachs, sickle cell anemia, Fragile X Syndrome, and Cystic Fibrosis. But in recent years, it has expanded beyond a small cluster of well-studied diseases into a much wider realm. As technology improved, expanded panels, which test for many diseases at once, entered the marketplace. They are, on their face, a good idea: more information at once, easier, and cheaper. But as the testing panels have become larger and more people test, this segment of prenatal care is changing radically.

Easier and cheaper

The rise in these tests “has changed the industry significantly,” said Blair Stevens, the National Society of Genetic Counselors' (NSGC) Prenatal Expert and a genetic counselor at McGovern Medical School at UTHealth. Before, because there were so few tests, most people were negative. Now, people are much more likely to come back with a positive hit on something, even though their partner is likely to be negative. The risk hasn’t changed, but the test has. And the test begets more tests.

In 2017, according to a paper in Nature, there were 13 companies offering expanded carrier screening with panels ranging from 100 to 300 conditions, and an estimated 200,000 people received expanded carrier screening in 2015. It has grown since then. The test I took was offered by a company called Counsyl, which was bought last year for $375 million in cash by Myriad Genetics. The current carrier test they offer, Foresight, has 176 conditions. According to Myriad, over one million patients have taken the test to date, and the company clocked a 7 percent increase in test volume last quarter. A similar test has even been offered direct-to-consumer, by 23andMe, where you can take a carrier screening test as part of your health results.

“In this prenatal genetic screening realm, it’s kind of a double edged sword,” Stevens said. “On the one hand I think the information is great and it is empowering to learn more. On the other hand it can be overwhelming.”

Carrier testing has gone from a procedure aimed at smaller subsets of the population to an often-integral part of prenatal care across ethnic groups and something experts urge women to consider. “It is recommended that all women who are pregnant or who are considering pregnancy should be offeredcarrier screening,” Stevens said. This testing should be done “ideally prior to conception” when the results create less anxiety. Patients can decide to make conception decisions based on the results, such as using in-vitro or a donor. But insurance companies aren’t always willing to cover the cost. And, as Jim Goldberg the chief medical officer from Myriad Women's Health, stressed to me, over half of pregnancies are unplanned. “We always recommend preconception testing. That being said, it doesn’t happen all that often,” Goldberg said.

Direct to consumers

Prenatal screening is a very competitive marketplace. Stevens told me that companies were marketing to her patients directly. Patients come into her office and ask about particular tests, especially the cell-free DNA test. The cfDNA screening has become a much more common way to screen for trisomy in early pregnancy, replacing the ultrasound-based nuchal translucency. It also has the bonus feature of identifying fetal sex long before the 20-week anatomy scan, making it incredibly attractive to expectant parents.

From a patient perspective, it also feels like a gateway into the prenatal marketing machine. After I took the cfDNA test, with a company called Natera, I began getting targeted emails about cord banking.

It also can prompt more screening. Many patients are offered the cfDNA and carrier screening in tandem, because it is easier for providers and often driven by contracts labs have with insurance providers. “Many labs that offer NIPT (non-invasive prenatal testing) also offer carrier screening because they realize the convenience that ordering both from one lab has on providers,” Stevens said. Myriad told me that they had offered the tests in together to thousands of patients over the last 12 months.

Competition within the marketplace has also led to larger and larger panels, sometimes with inaccurate results.

Stevens recommends panels that examine conditions that would significantly impact quality of life and have a high detection rate for each condition. In designing Foresight, Myriad said they examined 600 disorders for actionability, prevalence and sensitivity and ended up with 176 serious conditions that would impact quality of life severely.

The Foresight panel is much larger than what professional organizations like the NSGC and the American College of Medical Genetics recommend. According to Anthony Gregg, the president of the American College of Medical Genetics, there are two ways really to judge what conditions should be on a panel, carrier frequency, and severity of conditions. The recommendations set the frequency limit to 1 in 100 or 120 people at the most. “You get lots of different industries and companies citing what should and should not be on a panel. But there are the 40 conditions if you extend it out to 1 in 100 and 1 in 120. Beyond that the value is uncertain,” he said. Myriad contends that important conditions might be missed if their panel were smaller.

Gregg doesn’t advocate for retesting, which can happen when a patient is offered a panel again because it has been expanded. (This happened to me. Between my two pregnancies the panel grew.) Gregg also said he doesn’t advocate for taking the test yourself through a direct-to-consumer service. “I want to be really clear that this is medical testing and these types of results should be provided under the direction of a healthcare professional,” he said.

The knowledge gap

One other major issue is the “knowledge gap,” as Gregg put it. Care providers struggle to keep up with rapidly changing technology and rare genetic conditions they have never heard of. There are not enough genetic counselors to match the demand, they are not spread evenly across the country and sometimes aren’t affordable, even as tests get more ubiquitous.

It is a problem the companies like Myriad acknowledge and are trying to solve themselves, via online genetic counseling services – though I was hesitant to use it because it felt like they were trying to “sell” me genetic counseling through offering a complimentary consult. The companies, said Gregg “have filled the gap.”

“At this point in time though there’s no evidence to show there’s any bias in the information being conveyed...but I think it’s tricky and we should continue to ask that question over and over again,” he said.

This knowledge gap may increase as panels continue to grow and the tests on offer proliferate. Earlier this year Myriad announced the expansion of cfDNA test they do from the standard 5 chromosomes that were previously tested to all 23 pairs. “I do think the importance of pre-test counseling becomes increasingly important as the screening expands because expanded technology typically comes with increasing limitations,” Stevens said.

Experts such as Gregg, see a lot of value in having the information, especially if you find out your fetus could be affected. Maybe you make a decision to discontinue a pregnancy, educate yourself about the disease, or change your healthcare options, or just do nothing.

When I asked if their results could be read as too much data, Goldberg said patients were hungry for it. “To me, I look at it as, I like information. So for me providing and identifying the greatest number of couples at risk for the most serious disorders makes sense to me.”

But it is also targeting patients at an extremely vulnerable stage, when people would do basically anything to mitigate risk even when that risk can’t be completely understood or they lack help to understand it. I felt this so much during pregnancy: that I could or would do anything, but I didn’t always understand what that anything was. Gregg told me when he asks patients if they want more testing they often say: “Why are you asking me this? Of course, I would want anything that you could tell me.”

UPDATE: Aug. 29, 2019, 10:01 a.m. EDT A previous version of this article referred to Jim Goldberg as the chief medical officer from Myriad Genetics. He is the chief medical officer from Myriad Women's Health. Also, Myriad reported a seven percent increase in test volume, not sales.

最新评论