Trisomy test+ (13,18, 21, XY, microdeletion)
The TRISOMY test is a quick, easy, and safe method to learn more about the health of your unborn child. The 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, you should see a gynecologist and obstetrics specialist or a clinical geneticist. "Non-Invasive Prenatal Testing" (NIPT), offered by various laboratories, detects specific abnormalities of chromosome 21, 18, and 13, as well as abnormalities of the sex chromosomes. However, the results do not reveal any information about genetic or morphological fetal or maternal disorders other than those intended for detection. Positive test results from NIPT require invasive confirmation.
Trisomy 21 (Down syndrome) NIPT screening can detect more than 99% of cases of trisomy 21. Regarding the TRISOMY test, only 1 out of 1,842 results based on normal pregnancy was found to be a false positive (less than 0.05%). The results of a recent validation analysis involving a set of samples from pregnant women and a set of samples containing fetal trisomy 21 showed that the TRISOMY test is very sensitive.
Trisomy 18 (Edwards syndrome) NIPT sensitivity in detecting trisomy 18 is 90%. The coefficient of false positive results of the TRISOMY test is 0.01%. The coefficient of false negative TRISOMY test results (1 in 9 cases) is comparable to the global coefficient (1 in 10 cases).
Trisomy 13 (Patau syndrome) In a recent international analysis based on 11,185 samples, 2 out of 2 positive cases of trisomy 13 were successfully identified. The false positive rate for this type of trisomy in this particular analysis reached 0.02%. Regarding the TRISOMY test screening test, 3 out of 3 trisomies were correctly identified within 13 cases, with a false-positive rate of 0.05%.
Sex Chromosome Syndrome In international studies, syndromes associated with an abnormal number of sex chromosomes have detection rates of 93% and 90% for syndromes with an incidence rate of 1 in 490 (Klinefelter syndrome, XXX syndrome, and XYY syndrome) or 1 in 2700 (Turner syndrome), respectively. The false positive rates of these syndromes are as high as 0.14% and 0.23%, respectively, and the accuracy of the method is above 99% in both cases.
Microdeletion syndromes Detection rates for microdeletion aberrations reach 83% for deletion regions with more than 6 million bases and 20% for deletion regions up to 6 million bases when standard genomic sequencing is used.
The TRISOMY test is a non-invasive maternal blood test that can, thanks to its high sensitivity and specificity, rule out the presence of chromosomal abnormalities after the 11th week of pregnancy. It can also determine the sex of the unborn child if the expectant mother wishes to know it. The test is suitable for any pregnant woman as early as the 11th week of pregnancy and provides significantly fewer false positive results than traditional screening methods for the types of trisomy for which it is intended. The test is suitable for pregnant women who:
- are concerned about possible health problems in their unborn child due to the presence of one of the trisomy types under investigation;
- are 35 years of age or older at birth and have a negative biochemical screening test result;
- conceived through IVF;
- have a positive biochemical screening test result;
- have an ultrasound screening result indicating a higher risk of the trisomy types under investigation;
- have a history of fetus chromosomal abnormalities;
- their parent(s) have been diagnosed with a Robertsonian translocation (increased risk of trisomy 13 or 21);
- have a history of habitual non-pregnancy.
Medical and genetic counseling should be done before the test. The 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 level of blood clotting indices);
- immune risk due to Rh incompatibility (negative Rh factor);
- gestational age between 14 and 16 weeks of pregnancy (increased risk of complications caused by amniocentesis);
- placenta previa;
- uterine myoma.
Consult with your gynecologist/obstetrician about all obstetric contraindications. Before undergoing non-invasive prenatal testing, you should obtain a consultation with an obstetrician-gynecologist or clinical genetics specialist.
The results of non-invasive prenatal testing provide information about a select number of the most common genetic chromosomal disorders (up to 85% of all fetus genetic disorders). Testing cannot detect all existing genetic or developmental disorders. If your NIPT test results are negative, it can help you avoid invasive diagnostic tests such as amniocentesis, which carries certain risks associated with taking amniotic fluid. The sensitivity and specificity of the TRISOMY test are more than 99%.
Attention: Despite the high sensitivity and specificity in determining fetus trisomy by chromosomes 21, 18, and 13, the TRISOMY test is considered a type of screening, not a diagnostic method. Therefore, a positive result should always be confirmed by taking amniotic fluid or villous chorion. A negative TRISOMY test result does not have to be confirmed by diagnostic amniocentesis, which means that in most cases, the expectant mother can avoid invasive tests and their associated risks. If the result of the TRISOMY test is positive, it is necessary to consult with a genetics specialist, who will refer you to the examination necessary in this situation.