Prenatal Screening: Are all non-invasive prenatal tests the same?
Non-invasive prenatal testing (NIPT) using cell-free DNA allows for faster and more accurate screening than both the Quebec prenatal screening program for trisomy 21 and the different hormone-based screening tests offered in private clinics. NIPT using cell-free DNA is a test that can screen for multiple genetic anomalies from just one blood sample from the mother as early as the 10th week of pregnancy. These tests are reliable up to 99.9% and can provide results in the first trimester of pregnancy.
Different laboratories offer different tests depending on the private clinic you choose for your prenatal testing. But are all these tests the same? To answer this question, we asked the opinion of Andrea Secord, certified genetic counsellor. Here is her response: First, the efficiency of the test, the reliability of the results and the speed of the analysis will all be influenced by the DNA sequencing method and the location of the analysis. So that means that these tests are not all equivalent. Andrea recommends choosing a test that is analyzed in North America and whose method of sequencing allows the lowest failure rate. A failure in the analysis of the blood sample occurs when the laboratory is unable to provide a result. Some risk factors increase the rate of failure, including in vitro fertilization, maternal obesity and certain other medical conditions of the mother. In 22% of cases, a test failure hides a genetic anomaly, so the recommendation for such a situation is to refer the expectant mother for amniocentesis. The failure rate varies between 0.1% and 6% depending on the sequencing method and the chosen laboratory. Since the goal of NIPT is to avoid an amniocentesis, it is important to choose a test with a low failure rate.
Here are the questions that future parents should ask themselves before choosing a prenatal screening test by cell-free DNA:
– What is the failure rate of the test?
– How long does the analysis of the blood sample take?
– Where will the blood sample be analyzed?
– How will the results be given to future parents and to the health care professional following the pregnancy?
– How reliable are the results?
In order to support a free and informed choice, your health care professional should be able to answer these questions before referring you to a prenatal screening test using cell-free DNA.
The Premium Plus (Verifi) and Signature (Verifi+) tests offered by Prenato are reliable up to 99.9%, have a failure rate of 0.1% and are analyzed in California. The results are received on average in 5 working days and will be given to you directly by telephone by a Prenato nurse. A copy of your result will also be sent to your health care professional. If the result is abnormal, your health care professional will contact you to explain your result and the Prenato team will ensure your case will be taken care of quickly.
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Photo by Camylla Battani