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Similarities and differences between Double test - Triple test

The article was professionally consulted by MSc.BS expert by MSc Nguyen Thanh Vinh - Department of Obstetrics and Gynecology, Vinmec Ha Long International General Hospital.
Double test and Triple test are two very important tests during pregnancy to screen for fetal malformations. However, many pregnant women do not fully understand them. The following article will help mothers have a more detailed look at the similarities and differences of these two types of tests.

1. Similarity of Double test and Triple test

1.1. Purpose of testing

Both the Double test and the Triple test are performed in pregnant women to screen for the risk of genetic defects in the fetus.
One thing to note, both are not affirmative but only detect genetic abnormalities and indicate whether the risk of having the defect is high or low. High risk does not mean that the baby will definitely have a birth defect, on the contrary, a low risk does not mean that the fetus is completely normal.
Besides, when the results of the Double test and Triple test are positive (high risk of malformations), the doctor will order an amniocentesis test. This can help your doctor know exactly if your baby has Down syndrome.

1.2. Execution object

According to the recommendations of the Ministry of Health, pregnant women should do the Double test and Triple test. Especially for mothers in the following high-risk groups, it is even more important to do:
Pregnant over 35 years of age Have had a miscarriage or stillbirth of unknown cause Pregnancy history of genetic defects Family history Family with birth defects Diabetic Pregnant mother infected with virus during pregnancy After fetal ultrasound, if any abnormality is suspected, pregnant mother should perform Double test and Triple test.
Mẹ bầu nào cũng cần thực hiện Double test và Triple test
Mẹ bầu nào cũng cần thực hiện Double test và Triple test

1.3. Accuracy

Double test or Triple test both give accurate results up to 90%. However, every test has certain errors. Therefore, pregnant women should choose a reputable medical facility to perform fetal malformation screening.
Furthermore, actual test results and risk may differ because of many other subjective factors. For example, although with a single pregnancy, the accuracy of the Double test and Triple test can reach 90%, but for women pregnant with twins, the results are sometimes inaccurate. In addition, incorrect determination of gestational age also makes the results more or less misleading.

2. What is the difference between Double test and Triple test?

2.1. Implementation time

With the Double test: Pregnant women should do it when the fetus is 11 - 13 weeks old (corresponding to the length of the fetal buttock head from 45 - 84mm), preferably at the 12th week of pregnancy.
With the Triple test: Pregnant women should perform from the 15th to the 22nd week of pregnancy, most precisely at the 16th - 18th week.

2.2. Detectability

Double test or Triple test both help doctors determine the risk of fetal syndromes including: Down syndrome (excess chromosome 21), Trisomy 18 syndrome (excess chromosome 18).
Double test or Triple test both help doctors determine the risk of fetal Down syndrome
However, Double test can detect more Trisomy 13 syndrome (excess chromosome 13), while Triple test can find risk of neural tube defects.
Xét nghiệm Double test hay Triple test đều giúp bác sĩ xác định nguy cơ thai nhi mắc hội chứng Down
Xét nghiệm Double test hay Triple test đều giúp bác sĩ xác định nguy cơ thai nhi mắc hội chứng Down

2.3. Test kit

Double test test determines the concentration of 2 substances in the mother's blood secreted by the fetus:
PAPP-A (PAA): A glycoprotein produced from the placenta, free β-hCG (FBC): A component in the structure of the placenta. structure of hCG (human chorionic gonadotropin). Meanwhile, the Triple test test determines the concentration of 3 other substances in the mother's blood that are also secreted by the fetus, including:
AFP (Alpha-fetoprotein): A glycoprotein derived from the fetus. uE3 (Unconjugated estriol): Appears on the 8th day of pregnancy. β hCG (Beta human Chorionic Gonadotropin): A steroid produced by the placenta.

3. With the results of the Double test/Triple test in the high-risk group, what should pregnant women do?

With abnormal ultrasound results or Double test / Triple test results in the high-risk group, pregnant women should choose NIPT prenatal screening: NIPT prenatal screening has higher accuracy and detects fetal problems earlier.
Be consulted and choose NIPT / amniocentesis / chorionic villus biopsies. NIPT is a non-invasive prenatal screening test with high accuracy, possibly over 99% for Down syndrome.
Amniocentesis / chorionic villus biopsies are diagnostic procedures, but are risky and require careful pre-procedure counseling and preparation.
Below is a comparison table between prenatal screening methods:
Ưu điểm

4. Where should prenatal screening methods be done?

Currently, many medical facilities can perform prenatal screening methods. However, women should choose a reputable facility with a specialist in obstetrics and gynecology, a team of experienced and highly qualified doctors. Thus, it is possible to ensure the most accurate test results, but besides that, pregnant women are also given appropriate advice and care for the fetus during pregnancy as well as limiting complications.
Vinmec International General Hospital has a team of experienced experts who are professionally trained in the country and in countries with leading scientific development in the world such as Germany, UK, and France, who will provide advice on genetics. communicated to clients before making decisions about prenatal screening methods.
Triển khai NIPT.
Vinmec - Địa chỉ uy tín để sàng lọc trước sinh
With comprehensive fetal malformation screening packages at Vinmec, pregnant mothers are completely assured of the quality of services, giving fast, accurate results and outstanding safety. For more details, please make an appointment on the website to be served.

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