About TRISOMY testing
TRISOMY test is a non-invasive maternal blood test which can – thanks to its high sensitivity and specificity – exclude the presence of chromosomal abnormalities as early as in the 11th week of pregnancy. If the mother-to-be wishes to know, the test can also determine the sex of her unborn baby.
Compared to other screening methods, the TRISOMY test:
- has a higher sensitivity and specificity with regard to the disorders monitored,
- minimizes false positive results,
- reduces the number of necessary amniocenteses,
- poses no risk to either the mother or the child.
If the mother-to-be wishes to know, TRISOMY test can also determine the sex of her unborn baby.
Fetal DNA is already present in maternal blood in early stages of pregnancy. Thanks to a special screening laboratory procedure, it is possible to isolate and analyse foetal DNA to determine the risk of trisomy (three identical chromosomes).
Reliably
thanks to high sensitivity
Safely
without any sampling risks
Painlessly
using only maternal blood
Quickly
results available within few days
Timely
as early as in the 12th week of pregnancy
TRISOMY test will exclude
frequent chromosome number disorders (chromosome 21, 18 and 13 trisomy) *
detect
potential false positive results of biochemical prenatal screening tests.
minimise
the necessity of amniocentesis (invasive amniotic fluid sampling).
determine
the sex of your unborn baby, if you wish to know.
* the cause of Down, Edwards and Patau syndromes
Down Syndrome Detection Rate
1 The percentage indicates the number of positive results at a false positive rate of 4,5 %.
2 The percentage refers to Down syndrome and no other fetus defects.
3 In an extended validation study, TRISOMY test showed a sensitivity of 100% (95% Confidence Interval 83.89–100%) and a specificity of 99.95% (95% Confidence Interval 99.70–100%)
4 Compared to standard TRISOMY test screening, the detection sensitivity of TRISOMY test + is comparable, possibly even higher.
* In compliance with a resolution adopted by the Ethics Committee of the Slovak Ministry of Health, our laboratory only provides test results to patients once they have completed their 12th week of pregnancy. The test result is disclosed and interpreted to the patient by the doctor who referred the patient for the test.
Read more about the sensitivity of non-invasive prenatal testing (NIPT)
General information
Offered by various laboratories, non-invasive prenatal tests (NIPTs) detect specific chromosome 21, 18 and 13 and sex chromosome number abnormalities. The tests yield results that do not reveal any information on genetic or morphological foetal or maternal disorders other than those they are designed to target. Screen-positive NIPT results must be subsequently validated by analysing a sample obtained using an invasive method.
Trisomy 21 (Down syndrome)
NIPT screening can detect more than 99% of trisomy 21 cases. Generally speaking, only 1 in 1,650 trisomy 21 NIPT results based on normal pregnancies (0.06%)* has been identified as false positive. As for TRISOMY test, only 1 in 1,842 results based on normal pregnancies has been identified as false positive (i.e. less than 0.05%). The results of our latest validation study involving a set of samples obtained from pregnant women and a set of samples containing fetal trisomy 21 showed that our TRISOMY test is highly sensitive.
Trisomy 18 (Edwards syndrome)
The sensitivity of NIPTs for trisomy 18 is lower than their sensitivity for trisomy 21, namely 90%*. The false positive ratio is 0.01%*. TRISOMY test false negative result ratio (1 in 9 cases*) is comparable to the global ratio (1 in 10 cases*).
Trisomy 13 (Patau syndrome)
Prospective studies rarely include trisomy 13 cases, which makes NIPT sensitivity and specificity calculations for this type of syndrome rather difficult. In a recent international study based on 11,185 samples, 2 out of 2 positive cases were successfully identified*. The false positive ratio for this type of trisomy in this particular study reached 0.02%*. As for TRISOMY test screening, 3 out of 3 trisomy 13 cases were correctly identified, the false positive ratio being 0.05%.
* – DOI: 10.1056/nejmoa1407349#t=article
Sex chromosome syndrome
In international studies, syndromes associated with abnormal numbers of sex chromosomes, whose incidence rate is either 1 in 490 (Klinefelter syndrome, XXX syndrome, and XYY syndrome) or 1 in 2,700 (Turner syndrome), show detection ratios of 93% and 90%, respectively. The false positive ratios for the two groups of syndromes reach 0.14% and 0.23%, respectively, the accuracy of the method being higher than 99%** in both cases.
Microdeletion syndromes
Prospective studies rarely include microdeletion syndrome cases, which makes NIPT sensitivity and specificity calculations rather difficult. However, available data suggest that the detection rate for microdeletion aberrations reaches 83% for deletion scopes larger than 6 million bases and 20% for deletion scopes of up to 6 million bases on condition that standard genomic sequencing is applied (4-10 million readings per sample)***.
* DOI: 10.1056/nejmoa1407349#t=article
** DOI: 10.1002/uog.14791; DOI: 10.1186/1750-1172-1-42
*** DOI: 10.1016/j.ajhg.2015.11.016
Who is the TRISOMY test designed for?
TRISOMY test is suitable for any pregnant woman from the 11th week of pregnancy.
Compared to traditional screening methods, TRISOMY test has higher sensitivity and specificity rates for the detection of the trisomy types it is designed to monitor. As a result, it provides a significantly lower number of false positive results.
It is particularly suitable for pregnant women:
- who have concerns about their baby’s potential disability as a result of one of the trisomy types monitored;
- who are 35 or older at the time of childbirth and whose biochemical screening test results were negative (combined test, triple test, serum integrated test, integrated test);
- who conceived as a result of IVF;
- with positive biochemical screening results, which have to be confirmed by further testing (amniocentesis);*
- whose ultrasound screening test results suggest a higher risk of the trisomy types monitored,*
- who have already carried babies with a chromosomal abnormality before,*
- whose parent(s) has/have been diagnosed with Robertson balancing translocation (an increased trisomy 13 or 21 risk),*
- pregnant women who have suffered recurrent miscarriage.*
* The screening test must be preceded by a genetic consultation.
TRISOMY test is also advantageous in the event of gynaecological and obstetrical contraindications,** which may render invasive prenatal testing (amniocentesis) complicated, such as:
- increased miscarriage risks,
- ongoing anticoagulant treatment (impaired blood clotting),
- immunization risk due to Rh incompatibility (Rh-negative),
- the period between the 14th and the 16th weeks of pregnancy (increased risk of complications caused by amniocentesis),
- placenta praevia,
- uterine fibroids.
** Please, consult your gynaecologist/obstetrician about all obstetrical contraindications.
Before you decide to go ahead with non-invasive prenatal testing, consult your gynaecologist or a specialist in the field of clinical genetics. Ask them for more details about the purpose, advantages and potential risks involved, inquire about alternatives to TRISOMY test, and make sure you fully understand all the information provided.
Remember to inform your doctor about any relevant details related to your condition that might be decisive in choosing the most suitable healthcare procedure.
TRISOMY test and TRISOMY test + results
Non-invasive prenatal test results provide information about a selected number of the most frequently occurring genetic chromosomal disorders (up to 85 % of all foetal genetic disorders). It must be borne in mind that they cannot identify all existing genetic or developmental disorders.
If negative, NIPT test results can help you avoid invasive diagnostic testing, such as amniocentesis, which carries certain risks associated with amniotic fluid sampling.
Please note: Despite its high sensitivity and specificity in detecting fetal chromosome 21, 18 and 13 trisomy, TRISOMY test is considered a type of screening, not a diagnostic method. Consequently, a positive result must always be confirmed by amniocentesis or chorionic villi sampling.
A negative TRISOMY test result need not be confirmed by diagnostic amniocentesis, which means, in most cases, that the mother-to-be can avoid invasive tests and the risks they come with.
In the event that your TRISOMY test result is positive, you should arrange an appointment with a specialist in genetics, who will refer you for examinations required in the circumstances.
In a small percentage of cases, the method does not lead to unequivocal results and the laboratory analysis is concluded to be unsuccessful. In the circumstances, such results are labelled “non-informative”, i.e. of no diagnostic value. Chromosome analysis may be unsuccessful because of a low fetal DNA concentration in maternal blood. However, a low fetal DNA concentration in maternal blood is not to be understood as a reason for concerns as it occurs naturally in about 5% of all pregnant women. The concentration of fetal DNA gets progressively higher further on in pregnancy.
If a repeat examination based on the same blood sample yields a non-informative result, the mother-to-be will be advised to repeat the test 14 days later, which is free of charge and almost always leads to unequivocal test results.
*If a blood sample cannot be processed by the laboratory in accordance with the principles of good laboratory practice, or if the analytical results do not provide an answer to the diagnostic question, the laboratory offers a repeat examination based on the same blood sample free of charge (in the circumstances, the period for the delivery of test results will change from 5 to 8 days).
Praise for TRISOMYtest
Basic biochemical screening indicated some of my parameters were, due to my age, slightly higher, which made me feel uncertain and worried. That is why my husband and I decided to give TRISOMY test a try. One simple blood test and the results were in within a few days. The relief we felt when the doctor confirmed we were facing no risk was indescribable! And as a bonus, we learnt it's a baby girl. We’ve been using her first name since then, which brings the three of us even closer to one another.