As Non-Invasive Prenatal Testing (NIPT) is now offered at Premier Medical Laboratory Services, we want to offer resources for healthcare providers on the topic. In a recent GenomeWebinar sponsored by Illumina, Katie Ellis, Senior Genetic Counselor at Genea Fertility, discussed important issues to consider when ordering non-invasive prenatal screening. In the webinar, Dr. Ellis laid out the five things below that all providers need to know about offering NIPT to patients.
The first thing to know which needs to be relayed to patients is that cfDNA, or circulating cell-free DNA, are degraded DNA fragments released to the blood plasma. NIPT analyzes these fragments of maternal DNA and placental DNA during pregnancy, not fetal DNA. The test is not diagnostic but is used as a screening method. This means that the results cannot be used to give a definitive answer on whether the developing baby has or does not have a chromosomal abnormality. Rather, it provides information on the risk for fetal aneuploidy.
Secondly, the fetal fraction is the proportion of cfDNA in the blood that is placental and not maternal. Generally, the fetal fraction must be above 4 percent, which typically occurs around the tenth week of pregnancy. Low fetal fractions can lead to an inability to perform the test or a false negative result. Most commercial companies report the fetal fraction on the report. Fetal fraction can be affected by obesity, auto-immune conditions, certain medications, and certain aneuploidies. If there is a failure to report, the risk of fetal aneuploidy is ten times higher. If there is a failure to report, sometimes the answer is to wait a few weeks and recollect the sample
The third thing discussed in the webinar was that certain factors can lead to discordant results. These factors that lead to discordant results can be divided into two groups: fetal factors and maternal factors. The first fetal factor is low fetal fraction, which was just discussed. Another fetal factor is feto-placental mosaicism, which occurs when the fetus possesses more than one genetic line as the result of a genetic mutation. The last fetal factor is called the vanishing twin which happens when the NIPT detects the cfDNA from a demised co-twin up to 8 weeks after the loss. The maternal factors include maternal chromosome variation, maternal malignancy, and maternal transfusion or transplantation.
The fourth thing that providers need to be aware of is that there have been many new advancements in NIPT. Research and new developments are always evolving and expanding. It is important to know that different panels can now test for different conditions. It is now possible to do a microdeletion panel, look for a 22q deletion syndrome, and to detect rare autosomal aneuploidies.
Lastly, the fifth thing that a provider must do before offering NIPT to a patient is pre-test counseling. It is important to know what to do if the test fails, understand the turnaround time of results, find out the gestational age of the pregnancy, know if the parents want to discover the fetus’ sex, and what the test you are using screens for. Pre-test counseling also requires a provider to inform their patient. What does the mother want to know? Does she have the financial ability to go through with the test? Is she informed about other testing options or even that not being tested is an option? These are things that the provider must be able to ask and answer for the patient.
NIPT is an amazing technology that allows patients to know, risk-free and sooner than ever before, if their developing baby is at risk for common chromosomal abnormalities. To learn more about NIPT, watch the full video from the GenomeWebinar referenced below.