Trisomy test (13,18 и 21)
TRISOMY test is a quick, easy and safe way to learn more about the health of unborn baby. TRISOMY test is designed to rule out the most common genetic abnormalities (trisomies) of chromosomes 21, 18 and 13 that cause Down, Edwards and Patau syndromes. Before undergoing the test it is necessary to consult a Gynecological and Obstetric Specialist or a Clinical Geneticist.
Non-Invasive Prenatal Testing (NIPT), offered by various laboratories; NIPT defines specific abnormalities of chromosome 21, 18 and 13 and sex chromosomes abnormalities. The tests produce results that do not reveal any information about genetic or morphological fetal or maternal disorders other than those for which they are designed. Positive NIPT test results require invasive confirmation.
Trisomy 21 (Down syndrome)
NIPT screening can detect more than 99% of trisomy 21 cases. Overall, within NIPT results, only 1 in 1650 trisomy 21 cases based on normal pregnancy (0.06%)* was detected as a false positive. Regarding TRISOMY test, only 1 in 1,842 results based on normal pregnancy was identified as a false positive (i.e., less than 0.05%). The results of a recent validation study including a set of samples obtained from pregnant women and a set of samples containing embryonic trisomy 21 showed that the TRISOMY test is extremely sensitive.
Trisomy 18 (Edwards syndrome)
NIPT sensitivity in detecting trisomy 18 is lower than the sensitivity in detecting trisomy 21, precisely at the rate of 90%. The false positive rate of TRISOMY test is 0.01%. The false negative rate of TRISOMY test (1 in 9 cases*) is comparable to the global rate (1 in 10 cases*).
Trisomy 13 (Patau syndrome)
In prospective studies, cases of trisomy 13 are rare, which makes calculating the sensitivity and specificity of NIPT for this type of syndrome quite challenging. A recent international study based on 11185 samples successfully has identified 2 out of 2 positive cases*. The false positive rate for this type of trisomy in this particular study has reached 0.02%*. As for TRISOMY test, 3 out of 3 trisomies were correctly identified in 13 cases, with a false positive rate of 0.05%.
TRISOMY test is a non-invasive maternal blood test that can rule out the presence of chromosomal abnormalities already after the 11th week of pregnancy, due to its high sensitivity and specificity. The test can also determine the unborn child’s sex, if the expectant mother wishes to know it. TRISOMY test is suitable for any pregnant woman as early as the 11th week of pregnancy. Compared to traditional screening methods, TRISOMY test has a higher sensitivity and specificity for determining the types of trisomy for which it is designed. As a result, it provides significantly fewer false positives.
TRISOMY test is suitable for pregnant women who:
experience anxiety about possible health problems of the unborn child caused by the presence of one of the studied types of trisomy;
are 35 years old or older at delivery time and have a negative result of a biochemical screening test;
conceived a child as a result of IVF, have a positive result of biochemical screening*, received the result of an ultrasound screening examination indicating a higher risk of the monitored types of trisomy,*
in the past had a diagnosis of fetal chromosomal abnormality,*
their parent(s) was diagnosed with Robertson translocation (increased risk of trisomy 13 or 21),*
suffer from habitual miscarriage of pregnancy.*
- Before the test, it is required to undergo a medical and genetic consultation.
TRISOMY test is also convenient in case of gynecological and obstetric contraindications that may complicate invasive prenatal testing (amniocentesis), such as:
increased risk of miscarriage,
current anticoagulant therapy (low blood clotting indices),
immune risk due to Rh incompatibility (negative Rh factor),
gestational age - between 14th and 16th week of pregnancy (increased risk of complications caused by amniocentesis),
placenta previa,
uterine myoma.
Consult your Gynecologist/ Obstetrician about any obstetric contraindications.
Obstetrician/Gynaecologist or clinical geneticist should be consulted before undergoing non-invasive prenatal testing.
TRISOMY test results
The results of non-invasive prenatal testing provide information on a selected number of the most common genetic chromosomal disorders (up to 85% of all fetal genetic disorders).
It should also be taken in mind that testing cannot detect all existing genetic or developmental disorders.
If the NIPT test is negative, it can help you avoid invasive diagnostic tests such as amniocentesis, which carries certain risks associated with taking amniotic fluid.
Sensitivity and specificity of TRISOMY test is greater than 99%.
Note:
Despite its high sensitivity and specificity in detecting fetal trisomy on chromosomes 21, 18 and 13, TRISOMY test is considered a screening test and not a diagnostic test.
Therefore, a positive result should always be confirmed by amniotic fluid or chorionic villus sampling.
A negative TRISOMY test result does not have to be confirmed by a diagnostic amniocentesis, which means that in most cases the expectant mother can avoid invasive tests and their associated risks.
If TRISOMY test result is positive, it is required to consult a Geneticist who will refer the other for the tests needed to be undergone in this situation.