ShareHumans have DNA packed into a specific number of sets of chromosomes. It is 22 pairs + (XX)/(XY), i.e., 46 chromosomes, where XX is present in females and XY in males. However, in some cases, there can be an abnormality that results in more than the mentioned number of chromosomes. This results in the improper development of the baby. The presence of such abnormalities can be predicted through two hormone levels, and these are tested in a double marker test. Learn here in detail about the double marker test in pregnancy, the interpretation of the results, and other necessary aspects to be well-informed.
What is the Dual Marker Test?
The Double Marker Test, also known as the Dual Marker Test, is a test conducted on expectant mothers to identify the possibility of genetic problems in the developing baby. The double marker test in pregnancy is a prenatal or maternal serum screening that is performed during the first trimester or the first three months of pregnancy.
The dual marker blood test assesses the levels of two hormones in the mother’s blood. These are:
- Free beta-hCG (Human Chorionic Gonadotropin), which is a hormone produced by the placenta
- PAPP-A(Pregnancy Associated Plasma Protein-A), which is a protein associated with placenta development
Purpose and Price of Dual Marker Blood Test
It is a predictive, not diagnostic, test that helps in identifying the presence of risks associated with chromosomal abnormalities such as Down syndrome, Patau syndrome, and Edward syndrome. Predictive here means that the test offers insights into the risk estimate for the mentioned condition. The dual marker test price ranges between INR 2000 to 3000.
Procedure of Dual Marker Test
The dual marker test procedure simply involves drawing a blood sample from the pregnant mother to measure the levels of the mentioned two hormones, i.e., hCG and PAPP-A. The doctor will recommend this between 8 and 14 weeks of pregnancy. The best time for collecting blood samples lies between the 11th and 13th week of pregnancy. The dual marker test reports can be expected between 3 and 7 days.
It is a non-invasive blood test that, in combination with the mother’s age and ultrasound findings, helps assess the risk of chromosomal abnormalities. The ultrasound test is also referred to as the Nuchal Translucency (NT) scan and involves calculating the size of the clear (fluid-filled) space at the back of the baby’s neck.
Double Marker Test Normal Values and Its Interpretation
The double marker test normal values for the two hormones are as follows:
- Beta hCG: 25,700 to 288,000 mIU/ml for all age groups
- PAPP-A: 1 MoM for all age groups
The interpretation of the dual marker test is done based on the categorisation stated in the reports. There are three categories where the risk of chromosomal abnormality may lie, which are:
- Low risk: It marks the normal value and is represented as ‘Screen negative’ in reports. This result is stated if the risk ratio is 1:1000 or higher. It indicates a low risk of the baby having any abnormalities. However, it does not entirely rule out the possibility of any abnormality in the baby.
- Moderate and High risk: If the ratio lies between 1:10 and 1:250, the reports are categorised as ‘Screen positive’ and exhibit moderate to high-risk categories. In such cases, further testing is recommended, such as the Non-Invasive Prenatal Test (NIPT), amniocentesis, or chorionic villus sampling to confirm the presence of genetic issues.
Dual Marker Test and NT Scan
To get the best results, the dual marker test (blood test) is followed by the NT scan (ultrasound) during your first trimester. The information that is gathered in both the tests determine low, moderate, or high-risk of abnormalities.
The NT scan is usually less effective without the dual marker test at detecting potential abnormalities. The ultrasound collects a real-time image of your baby. According to the International Journal of Reproduction, the dual marker test has a sensitivity around 50% and a specificity of 85.94% for detecting chromosomal abnormalities. NT scan when combined with dual marker test increases the accuracy rate up to 80 to 85%.
Conclusion
The dual marker test, or double marker test, is a predictive test conducted in pregnancy. This test is used to identify the presence of chromosomal abnormalities, i.e., an increase in the number of chromosomes. The tests are helpful in identifying the risk levels but do not confirm the presence of such abnormalities.
They need to be accompanied by further screenings to confirm the presence of such issues. If you are an expecting mother and seek expert care and guidance, Hinduja Hospital, Mahim, is right here. Book an appointment now to experience quality facilities.
FAQs
Can chromosomal abnormalities be treated?
No, chromosomal abnormalities can not be treated. However, testing offers insights into the possible results. The positive results help mentally prepare for the outcomes and improve the quality of life for the baby. It also helps take additional care for the pregnancy to ensure a successful delivery. On the other hand, negative results help relieve the anxiety regarding the baby’s health.
Are there limitations to the dual marker test?
Yes, there are limitations to the dual marker blood test. It should be understood that the dual marker test is a screening or predictive test and not diagnostic. The findings require further aid through other testing methods for confirmation. Further, the false-positive and false-negative results may also interfere with actual results.
Is the double marker test 100% accurate?
Since the double marker test is not a diagnostic tool and cannot confirm chromosomal abnormalities, it is not considered a 100% accurate test.
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