By Allison Proffitt
October 7, 2013
| The field of non-invasive prenatal testing is rapidly advancing thanks to tests from groups like Natera
, Berry Genomics
, Verinata, recently acquired by Illumina
, and others. Using cell-free DNA and circulating fetal cells, researchers are able to predict diseases more accurately than ever before.
At the Advances in Prenatal Molecular Diagnostics event last month in Boston*, a panel of experts closed two days of talks with predictions of where prenatal molecular diagnostics will go in the next three to five years.
All of the speakers agreed that the field is moving so rapidly, it’s hard—even for obstetricians—to keep up. Diana Bianchi, with Tufts University School of Medicine
, predicted that as tests for various trisomies and other fetal abnormalities become more common and more accurate, there will be a shift in the parental perception of “normal” (see, “In Conversation
With education, Ronald Wapner, of Columbia University Medical Center, hoped that there would be a tide change in the way that test results were interpreted by patients and their doctors. “We really need to stop thinking about prenatal diagnosis as having either two options: you have an abnormal result and you either continue the pregnancy or you terminate the pregnancy. We are way too sophisticated!” Ron stressed that these tests could give more actionable information. “We can give people information about their child and they won’t use that information to make a decision about terminating, but they’ll use that information to decide about early intervention.”
David Ledbetter, of Geisinger Health Systems, said his favorite point from the event was that based on the chromosome microarray data prenatally, in the general population all pregnancies should be considered high risk pregnancies. “The goal over the next few years,” he continued, “is to move to sub-chromosomal level, copy number variation with high reliability” tests. Within a few years, Ledbetter predicted that the body of data would grow on severity and clinical presentation associated with microduplications and microdeletions. “The value of that, is to determine what the child’s potential behavioral and medical risks are to be able to monitor and intervene early in those cases.”
Joe Leigh Simpson, of the March of Dimes Foundation, agreed that sub-chromosomal-level testing on every pregnancy would be ideal, but doubted the likelihood of that becoming mainstream within the next three to five years. “Unless we can get a Madison Avenue [advertising] package to explain what microdeletions and microduplications are, we’re not going to get there.” Cell-free DNA tests for selected trisomies is dominating the conversation, Simpson said. It warns parents about Down’s Syndrome, a condition that they recognize and fear. “When we get to deletion syndromes that have a numerical and alphabetical name sixteen feet long, and it’s totally archaic,” he said. “We’ve got to start with something that the public realizes is bad.”
“I’m actually relieved to hear what David said,” said Bianchi. “It’s a lot easier to come up with a panel of microduplications and microdeletions that have clinical consequences, and then perhaps a group of experts can get together and decide where the line is. What are the things that most couples would want to know about, or should know about because they’re actionable.”
As with all types of genomic tests, the panelists stressed the need for more education and for care in how results are delivered. Obstetricians don’t have the time to fully explain these types of tests, said Wapner. “We cannot talk to four million women in an hour!” he said, indicating the number of pregnant women in the US.
Wapner argued for a range of options and methods for educating the public including group counseling, though he acknowledged that group counseling is difficult. “We have to go outside of our discipline,” he said. “People do health literacy all the time and are good at it! We need research on the best way to counsel patients. What do they really want.”
Lisa Demers, a Certified Genetic Counselor with the Prenatal Diagnostics Program at Dartmouth Hitchcock in Nashua, New Hampshire, spoke from the audience calling for physicians to include genetic counselors in the process—inviting them to patient discussions, whether in groups or one on one. “I wish obstetricians would call on us and ask for help!” she said.
The field is moving too quickly for even Web education tools, Demers said. By the time a detailed education product has been created, whether website or video, there is new information available.
The field also needs to consider a larger audience. Bianchi pointed out that 50% of pregnancies are unplanned, and the rate of babies born into established marriages is going down. “There’s a certain casualness, now, to reproduction. We’re going to have to think in multiple strategies.” Wapner agreed, and encouraged the field to think of education for all women, not just in the first eight weeks of pregnancy. A universal carrier test should not be offered to pregnant women, but to all women by their gynecologist, he said.
Even for all the progress made in the field, none of the panelists believed that traditional, invasive tests would fall by the wayside soon. “The brochures that we saw in the hallway [for various prenatal products] are not going to say, ‘test’ for litigious reasons if nothing else,” said Simpson. “You could make the claim that intact fetal cells are no different from CVS [chorionic villus sampling], and in that sense, it is a test… but initially it’s going to be a screen.”
Cell-free DNA sequencing tests only detect trisomies in three chromosomes where the most common genetic defects occur (chromosomes 21, 13, and 18). Many women who get negative results from the cell-free DNA tests assume that it means their baby is fine, but invasive tests use chromosomal microarrays that also detect micro-insertions and micro-deletions that can have dramatic health consequences.
Invasive tests will go away eventually, said Arthur Beaudet, of Baylor College of Medicine, who chaired the panel. “But if you council a woman that it’s reasonable to stop at this point, you have to tell her that there are severe things that could be detected with invasive tests that a non-invasive test can’t yet detect.”
Bianchi agreed. “There’s no difference from a cell free DNA perspective, what you’re counting whether it’s a whole chromosome or some sub-chromosome because you’re looking for a balance against a reference. And we’re still using counting statistics, so it can’t be diagnostic… it’s still a screen, it’s just now you’re looking across the entire genome… I do believe, and I do counsel people, that they do need to follow up with an invasive procedure.