Comparing and contrasting Chromosome tests
With three different prenatal tests now available, it can be difficult to know which one is best for you and your baby. To help clear up some of the confusion, we have asked The Portland Hospital’s Lead Sonographer, Dean Meredith to compare the Non Invasive Prenatal Tests (NIPT) available at The Portland Hospital.
What NIPT tests are available at The Portland Hospital?
The two NIPT tests that are available at The Portland Hospital are known by their brand names, Harmony™ and Panorama™. Both estimate a foetus’ risk of having a chromosomal abnormality and have absolutely no risk to the mother or the baby.
How does Harmony™ work?
During pregnancy, expectant mothers have the genetic material of their baby (fetal DNA and RNA) circulating in their blood. Harmony™ takes a small sample of the mother’s blood and analyses the chromosomes present in the fetal DNA for abnormalities. It is available for women expecting a single baby and can be performed from 10 weeks gestations with the results expected approximately 14 days later.
What does Harmony™ test for?
Harmony™ screens the fetal DNA in the mother’s blood for Trisomies. Humans have 23 pairs of chromosomes and a Trisomy occurs when there are three copies of a given chromosome instead of the expected pair. There are many different types of Trisomy, but those screened for by Harmony™ are Trisomy 21 (Down’s Syndrome), Trisomy 18 (Edward’s Syndrome) and Trisomy 13 (Patau’s Syndrome).
Harmony™ is also used to test for the chromosomal abnormality, Monosomy X. This condition is also known as Turner’s Syndrome and develops in female foetus’ who have one X chromosome instead of the expected pair.
How accurate is Harmony ™?
Harmony is highly accurate. It detects 99% of all pregnancies with Trisomy 21, 98% of pregnancies with Trisomy 18, 80% of pregnancies with Trisomy 13 and 96.7% of pregnancies with Turner’s Syndrome. In comparison, traditional Down’s Syndrome screening tests have a detection rate of 75-95% which means that every 5-25 out of 100 pregnancy’s with Trisomy 21 will be missed.
What is Panorama™ and how does it differ from other NIPT’s?
Much like Harmony ™, Panorama™ is a NIPT that screens the fetal DNA in the mother’s blood for signs of chromosomal abnormalities. It can be undertaken earlier than Harmony™ from 9 weeks gestation and the results are usually available within 10-14 calendar days. Panorama testing also benefits from being the only NIPT test available that can detect the chromosomal condition, Triplody. Children with Triplody have 69 chromosomes instead of the expected 46 which can affect the development of their vital organs.
How accurate is Panorama™?
Slightly more accurate than Harmony™, Panorama™ testing is 99% accurate in detecting Triplody, Down, Edwards and Patau Syndromes. It is also 91.7% effective in detecting Turner’s Syndrome.
My NIPT test has proved positive. Where can I go for more information?
The only way to find out for certain if a foetus has a chromosomal abnormality is to undergo an invasive procedure such as Chorionic Villus Sampling or Amniocentesis. Should your NIPT indicate that your baby has a high risk of a chromosomal abnormality you will be invited to undergo one of these procedures.
For further information or to book an NIPT, Chorionic Villus Sampling or Amniocentesis test please contact the Ultrasound Department at The Portland Hospital on 0207 390 6351.