Tips for Navigating Prenatal Genetic Testing

August 14, 2014

Amniocentesis, CVS, noninvasive prenatal testing, microarray . . . the rapid advancements in prenatal genetic testing can be dizzying. These 7 expert tips can help navigate the gamut.

Rapid advancements in genetic testing have hit the prenatal world, prompting a number of changes already and promising additional developments in the coming years.

Even as the number of women undergoing amniocentesis or chorionic villus sampling (CVS) has declined, the emergence of chromosomal microarray to replace karyotyping has yielded a chromosomal windfall of sorts with many more details coming from a single screening test. What to do with the information, and which patients benefit from having a test that not all insurance companies cover, creates a combination of logistical and clinical decisions for patients and providers to navigate.

On the screening side, improved accuracy and the ability to check risk factors for an increasing number of genetic disorders has also posed challenges with affordability and which patients would benefit.

Keeping pace can be a dizzying experience for a fetal-medicine specialist, let alone for a general obstetrician who is responsible for the overall care of their pregnant patients.

“The provider is in a tough situation, and understanding all of this is really complicated,” said Mary Norton, MD, University of California, San Francisco, Division of Maternal Fetal Medicine, Department of Obstetrics, Gynecology and Reproductive Sciences. That the professional organizations are still sorting out the best standard practices as they seek to keep pace with the latest advancements and the wait for well-designed scientific studies, only magnifies the situation, she said.

When it comes to screening, there are three main tips experts want clinicians to keep in mind:

1. Remember the importance of traditional serum marker testing

Often lost in the conversation over the next best genetic test is the importance and reliability of the traditional serum marker blood screenings that have served patients and physicians well for years, said Norton, who is also a past board member of the Society for Maternal-Fetal Medicine.

While much of the focus has revolved around the accuracy of detecting Down syndrome, the fear has been that if new cell-free DNA screenings replace the traditional tests, some useful information for the care of mother and baby will be lost, Norton said. Besides giving a risk factor for Down syndrome, the traditional test can detect other obstetrical complications, such as preeclampsia and risk of premature delivery.

"Those two are much larger contributors to poor pregnancy outcomes than Down syndrome,” Norton said. “While we don’t have great ways to prevent them, knowing the risk can provide information that providers have come to rely on in figuring out who is at high risk.”

2. Understand the NIPT evolution

While advancements in NIPT using fetal DNA from the mother’s blood can detect nearly all cases of Down syndrome – returning false-positive results in fewer than 1% of cases – there are slight differences in how each of the four laboratories conduct the tests, said Jennifer Hoskovec, president of the National Society of Genetic Counselors.

“It is very important if an OB is doing the screenings in their office to understand what each lab offers in comparisons to others,” she said.

Plus, she said the labs are regularly changing their screenings, coming out with slightly newer versions. The nuances are important to evaluate for our understanding of the science behind the screenings and ensuring that the evidence is supported by peer-reviewed research.

“It is very much a moving target because the technology is moving so rapidly,” she said.

In addition, NIPT is expensive and, while it may be a good secondary screening test for those at high risk for Down syndrome, more research and development needs to happen to improve the gene sequencing provided in the results, Norton said.

3. Blood tests are not diagnostic tests

Even with improved accuracy, NIPT and traditional blood tests are not on the verge of replacing diagnostic testing. CVS or amniocentesis are the only means to diagnose a chromosomal disorder. The message, while obvious to many, is one that has been lost in the hype surrounding the improvements to noninvasive testing, said Michelle Strecker, director of genetic counseling services for CombiMatrix one of the clinical diagnostic laboratories specializing in cytogenomic diagnostic testing.

Microarray results have proved screenings incorrect, she said. “It is not melodramatic to say that several times we have prevented terminations of babies who end up being healthy. Basically you save a life.”

Microarray

Advances in cytogenomic testing through microarray have unleashed a number of challenges that experts say are important to understand in discussing the prenatal genetic testing with any patient.

Interest in microarray has increased, especially with the attention gained with the National Institutes of Health studies published in late 2012 in the New England Journal of Medicine and the subsequent recommendation from the American College of Obstetricians and Gynecology in December 2013 supporting its use in addition to or in lieu of karyotyping for prenatal testing of at-risk pregnancies.

Below are four tips to help navigate microarray:

1. Labs differ in technology

As with the uniqueness of NIPT hailing from different laboratories, microarray also is conducted differently depending on the lab, said Mark McDonough, CEO of CombiMatrix, noting that there are three different systems used for providing the data results.

2. Age doesn’t matter

While pregnant women older than 35 have been the traditional target for amniocentesis, the technology revolution has steered away from focusing on a woman’s age as a risk factor, all of the experts said. The American Medical Association has said that, regardless of age, everyone should be given the option of having an invasive diagnostic test.

3. Financial considerations are nuanced and paramount

Laboratories such as CombiMatrix offer maximum out-of-pocket rates for patients to help offset the fact that many insurance companies won’t cover the tests. But Hoskovec cautioned that state laws may get in the way. In Texas, for example, where she lives and works, these deals are illegal.

Furthermore, Norton said that often the out-of-pocket maximums can’t be applied to patients with high deductibles whose insurances companies have negotiated a rate and will approve the test.

“The truth of the matter is some of these tests may cost as much as the entire bill for the rest of prenatal care including delivery,” she said.

Obtaining preauthorization for patients from insurances companies is a must when dealing with microarray, Hoskovec said, noting that mostly insurance companies are looking for appropriate utilization of the test and if there is a medical need for conducting the test.

4. Consulting a genetic counselor is a must

Genetic counselors are increasingly integral to navigating the decision to test, whether or not to have microarray, and interpreting the results. Hoskovec said in understanding the science, the results, and the uniqueness of each laboratory, physicians should consult with genetic counselors not only within the community but also at the labs.

Strecker, at CombiMatrix, said her favorite part of the job is the consulting and counseling she is able to provide about individual results so physicians can communicate accurately with patients.

The complexities of the results and the sheer amount of information provided can be empowering, but only if it is properly understood, she said.

Testing Overload

Finally, a caution: Beware of testing overload.

“Right now, a lot of people are doing everything because they don’t know which test to do, and that doesn’t make a lot sense either,” Norton said.

“I think the majority of patients just want a healthy baby,” she said. “They get pregnant and are interested if it's a boy or girl and they are not that worried about much else. They just want a test to make sure everything is okay and are happy to have a blood test.”

The responsibility of providers is to ensure they are properly educating patients about the new tests, such as cell-free DNA and microarray, to ensure that they aren’t just feeding people mindlessly into the publicity trap of having the latest and greatest, Hoskovec said.

“What’s more important is how we offer testing,” she said. “Regardless of background risk, providers need to be having a conversation with patients about what kind of information they want about the pregnancy, talking about what tests can and can’t do, and making sure the patient is making an informed decision.”