- How do I arrange to have the Harmony™ non-invasive prenatal test (NIPT)?
- What information can NIPT provide?
- When is NIPT done?
- What are the benefits of NIPT?
- What are the down sides of NIPT?
- Who should have NIPT?
- Will NIPT replace amniocentesis and CVS?
- How do I get further information about this test?
Specialist Women's Ultrasound offers the Harmony™ non-invasive prenatal test (NIPT). Testing is performed in Melbourne; most patients will receive their results within one week of sample collection.
The test costs $460. This cost includes pre-test genetic counselling; taking of the blood sample; transfer of the sample to the laboratory; communication of the results to the patient and treating Doctor.
How do I arrange to have the Harmony™ non-invasive prenatal test (NIPT)?
An appointment is required in order to have the Harmony™ test. Please phone the practice on 9898 9055 to book a time. If you have questions about the test, or are considering whether the test is appropriate for you, please ask to speak to our Genetic Counsellor.
What information can NIPT provide?
The Harmony test can detect approximately 99% of fetuses affected with Down syndrome (Trisomy 21), 98% of fetuses with Trisomy 18, and a large number of pregnancies with Trisomy 13. The Harmony™ test can also look at the fetal sex and detect abnormal numbers of the sex chromosomes.
When is NIPT done?
The blood test can be taken any time from 10 weeks of gestation and can be performed in single and multiple pregnancies.
What are the benefits of NIPT?
The test has a higher detection rate for Down syndrome compared to the 12 week nuchal translucency scan. NIPT also has a lower false positive rate, meaning that fewer patients would be recommended to have amniocentesis or chorionic villous sampling (CVS) to confirm a high risk result. The NIPT test is a blood test, which is completely safe to the fetus with no risk of miscarriage.
What are the down sides of NIPT?
There are a number of potential pitfalls compared to more established tests such as the 12 week nuchal translucency scan and combined first trimester screening test. Because of these limitations, counselling prior to the test is highly recommended in order to determine if the test is appropriate for your circumstances.
- The test does not involve an ultrasound, and therefore does not look at the fetus. At the nuchal translucency ultrasound it is estimated that about 60% of major structural (but non chromosomal abnormalities) abnormalities can be detected. Patients who do choose to have NIPT should still have an ultrasound around 12-13 weeks to look for anatomical problems.
- The test only looks for Down syndrome, Trisomy 18 and Trisomy 13, and some laboratories also look at the sex chromosomes. It is estimated that these findings only account for about 70% of the major chromosomal abnormalities. This is in contrast to the nuchal translucency scan where, although the results are expressed as a risk for Down syndrome and Trisomy 18/13 we know that a thick nuchal translucency can occur in a large number of other chromosomal and non-chromosomal abnormalities.
- The test is a screening test and has a false positive rate. This means that if the test is high risk then an amniocentesis or CVS would be suggested to confirm the diagnosis. This also means that there is still a chance of the baby having Down syndrome if the NIPT result is low risk.
- There is a 1-4% test failure rate – meaning that sometimes the laboratory is unable to give you a result from the first blood collection.
Who should have NIPT?
NIPT is not recommended for everyone due to its limitations and costs. This test is a screening test, not diagnostic, and is not able to provide a definite ‘yes or no’ result for Down syndrome. Patients who receive a high risk NIPT result would be recommended to have an invasive test such as amniocentesis to confirm the diagnosis. Patients who receive a low risk NIPT result still have a small chance that their baby has Down syndrome.
Some patients, after a discussion about the pros and cons of the test with our Genetic Counsellor and/or their doctor, may choose to have the NIPT test performed before the 12 week nuchal translucency ultrasound. It is important to remember that even with a low risk result from NIPT, an ultrasound at 12 weeks is still recommended.
Patients may be offered the test following the combined first trimester screening test (ultrasound and blood test), using the combined results to guide management and decisions about NIPT. The nuchal translucency ultrasound risk assessment is performed between 12-13 weeks, and combined with the 10 week maternal serum screening blood test (as is current accepted practice). The combined screening result can be used to guide further management.
- Increased risk (risk greater than 1 in 50): offer CVS/amniocentesis. This is the risk range which has the highest chance of having a chromosome abnormality, Down syndrome or otherwise, many of which would not be detected through NIPT.
- Increased risk (1 in 50 to 1 in 300 risk): offer CVS/amniocentesis or NIPT. This is the risk range where most of the false positive results of the first trimester screening test occur. CVS or amniocentesis would provide certainty about chromosome abnormalities but have a low risk of causing miscarriage. Patients who want to avoid this risk may opt for NIPT. If the NIPT result is high risk, then an amniocentesis would be recommended to confirm the diagnosis.
- Low risk (1 in 300 to 1 in 1000 risk): offer NIPT. This is the low risk range where most of the false negative results from the first trimester screening test will occur (missed cases of Down syndrome). You may consider having NIPT to try to detect these cases.
- Low risk (risk less than 1 in 1000): suggest no further testing. The chance of having a baby with Down syndrome after a result in this range is very low indeed.
Will NIPT replace amniocentesis and CVS?
For some patients a low risk NIPT result is reassuring and they will not go on to have an invasive test (CVS or amniocentesis). NIPT will not replace these tests, however, as an invasive test is suggested if the NIPT result is high risk in order to confirm the suspected diagnosis. Chromosome results from CVS or amniocentesis are able to detect a very large number of abnormalities in all the 23 pairs of chromosomes, compared with NIPT which can only detect if there is an extra copy of 3 – 5 of the chromosomes.
How do I get further information about this test?
Please contact Specialist Women’s Ultrasound on 9898 9055 and ask to speak to our Genetic Counsellor for further information and discussion about this and other testing options for Down syndrome and chromosome abnormalities. It is recommended to have a detailed discussion about NIPT prior to having the test, to ensure you understand what is involved with this test.