Non-invasive prenatal test alternative to amniocentesis
1. What are NACE and NACE Extended 24?
NACE and NACE Extended 24 are non-invasive prenatal tests. This means that they are completely safe for you and your baby. A small blood sample taken from the arm, just like in any other routine blood analysis, is sufficient to run the test.
NACE and NACE Extended 24 use the latest sequencing technology to analyze fetal DNA compared to maternal DNA to detect certain anomalies with high precision and reliability. Reports provide Fetal Fraction Estimate that refers to the proportion of free DNA in circulation that belongs to the placenta, in relation to the total amount of free DNA in circulation found in the blood sample.
2. What are NACE and NACE Extended 24 useful for?
Human beings have 23 pairs of chromosomes with a total of 46 (two copies of each pair). Health and development issues appear if there is a missing or extra chromosome. When there is an additional copy of a chromosome (i.e. three copies instead of two), it is called a trisomy.
NACE is a complete prenatal test to detect anomalies in chromosomes 21, 18, and 13 (Down, Edwards, and Patau syndromes). It also detects the most common anomalies in the sexual chromosomes X and Y (Except for twin gestations).
NACE Extended 24 has the same characteristics as the NACE test, but is an extended version that also incorporates the detection of all 24 chromosomes and identifies six microdeletions which are associated with major genetic syndromes: DiGeorge syndrome, 1p36 deletion syndrome, Angelman syndrome**, Prader-Willi syndrome**, Cri-du-chat syndrome, and Wolf-Hirschhorn syndrome.
Both tests detect foetuses with chromosomal anomalies with very high precision.
3. For whom are NACE and NACE Extended 24 indicated?
These tests are recommended for women who want to rule out the most commonly detected fetal chromosomal alterations without putting their pregnancy at risk. They are especially recommended for women with a high risk of chromosomal abnormalities after first trimester screening, those with previous Down syndrome pregnancies, or to detect any alterations suspected from ultrasounds.
NACE and NACE Extended 24 can also be used by women whose pregnancy was achieved via in vitro fertilization, including gestations resulting from donated oocytes.
The NACE test is valid in single and twin* gestations and NACE Extended 24 is validated for single pregnancies.
*In these cases it does not provide information on the gender of the fetuses.
4. How to get the NACE test step by step
1. Call +971 4 5519465 to obtain information and ask for the test. Consult with your gynecologist.
2. You will receive the NACE kit.
3. A blood sample will be taken.
4. Igenomix will collect the kit with the patient’s blood sample.
5. Igenomix will deliver the test results as soon as they are available.
1. What are the differences with the anomalies detected by an amniocentesis?
At the chromosomal level, NACE detects anomalies in the number of chromosomes, not in their structure. It only detects anomalies for a limited number of chromosomes related with problems in gestations after the second trimester of pregnancy.
NACE Extended 24 incorporates the detection of all 24 chromosomes and identifies six microdeletions which are associated with major genetic syndromes: DiGeorge syndrome, 1p36 deletion syndrome, Angelman syndrome**, Prader-Willi syndrome**, Cri-du-chat syndrome, and Wolf-Hirschhorn syndrome.
2. Can a NACE test be done following a transfusion? How long do I have to wait after a transfusion to perform the test?
If the transfusion was with complete blood you should wait a minimum of six weeks after the transfusion for the NACE test blood extraction.
If you were transfused only with red cells, these do not contain a nucleus or DNA.
In trauma interventions where a lot of blood is transfused the presence of donated leukocytes has been detected up to a year and a half later.
3. Can the NACE test be done with donated oocytes? What about when using a surrogate uterus?
Yes, the test can be done in both cases.
4. Can the study be done in twin gestations?
Only the NACE test, not the NACE Extended 24 test can be done, and bearing in mind that in these cases we cannot provide information on the fetal sexes, or about any alterations in sexual chromosomes; the test only informs about the presence or the absence of a Y chromosome.
5. Can the test be done in gestations with twin embolization syndrome?
If the sack has disappeared the NACE test can be indicated; however, it should be noted that DNA originating from the reabsorbed sack could remain in the maternal blood; this could result in a false positive regarding the chromosome number in the viable fetus.
If the sack remains (although it hasn’t developed) the NACE test should not be indicated.
The probability that the sack has disappeared is very high although there is still an elevated risk that the test could produce a false positive if the other fetus had disappeared not long before performing the test, given that quite a lot of DNA from the other fetus will still remain present.
Currently, there isn’t any empirical data which can confirm the percentage risk or lowest levels of sensitivity of the test in these cases – it is a possible scenario because the DNA analyzed comes from the placenta.
6. What happens if a NACE or NACE Extended 24 test gives a positive result?
An amniocentesis or chorionic villus biopsy should be carried out. Occasionally, in cases of arrested pregnancy conventional curettage is performed. The chromosomal analysis performed depends on the alteration found and may be:
Conventional karyotype: which will serve to confirm/discard complete or partial aneuploidies in any chromosome as well as results suggestive of mosaicism.
Quantitative fluorescent polymerase chain reaction (QF-PCR): to discard/confirm aneuploidies of chromosomes 13, 18, 21, or sexual chromosomes.
Fluorescent in situ hybridization (FISH) and/or short tandem repeat (STR) analysis: to discard/confirm aneuploidies of chromosomes 9 or 16.
FISH and/or microarray-based comparative genomic hybridization (array CGH): to discard/confirm some microdeletions.
7. What happens if the fetal sex result from the NACE test isn’t the same as the ultrasound results?
A new maternal blood sample should be taken in a Streck tube and the Igenomix laboratories will determine the fetal sex (free of charge).