The development of a foetus can be affected by various chromosomal defects, which can lead to many complications in the fetus. These anomalies can result from structural flaws in the chromosomes, an inappropriate quantity of genetic material contained in a particular chromosome, or an imbalance in the number of chromosomes. Congenital defects, chromosomal diseases, and even miscarriages can result from the presence of these deformities. The use of the double marker or dual marker test helps identify such foetal anomalies, which, if left undetected, can lead to postnatal deformities in the infant.

What is a Double Marker Test?

The double marker test,  also known as the Maternal serum screening, is a more in-depth screening test that is part of a larger first trimester screening program. The double marker test is a predictive test, meaning that its results indicate the probability of chromosomal abnormality. The dual marker test in pregnancy looks for blood levels of two different markers: Beta-hCG (beta-human chorionic gonadotropin) and PAPP-A (Pregnancy-Associated Plasma Protein A). 

Elevated levels of beta-hCG are often associated with an increased risk of chromosome disorders. In order to identify any anomalies early on and prevent several health issues for the unborn child, doctors usually encourage patients to have this test performed in the first trimester.

Purpose of Double Marker Test

The double marker test is one of the most important tests for detecting the presence of a certain type of chromosome abnormality during pregnancy, which helps to avoid several postnatal health issues. This test assists in the detection of chromosomal anomalies in the developing foetus. Generally, a female foetus is composed of 22 pairs of XX Chromosomes, whereas a male foetus typically has 22 pairs of XY chromosomes. However, in rare cases, an abnormal chromosome may be present in all or some of the body's cells, resulting in a genetic condition known as trisomy. 

In such cases, the foetus may have three copies of the abnormal chromosome instead of two. This can lead to developmental deformities, delayed milestones or subnormal intelligence in the unborn child. Determining whether there are any chromosomal abnormalities using a double marker test for pregnancy can therefore be advantageous for both the mother and the unborn child.

What happens during the Double Marker Test?

The double marker test consists of a blood sample and ultrasound examination that analyses two markers: free beta hCG and pregnancy-related plasma protein A (PAPP-A). Free beta-hCG is a hormone secreted by the placenta in pregnant women, and a high value of this hormone is linked to an increased risk of Trisomy-18 and Down syndrome. PAPP-A, on the other hand, is a plasma protein that is essential for the functioning of the body. Having Down syndrome is more likely when there are low plasma protein levels. The double marker test findings are categorised as Positive, High-risk, and Negative.

Doctors encourage women over 35 and those with a family history of birth defects to get this test since they are more likely to have a chromosome abnormality, which can result in a chromosomal malformation in the developing baby.

Procedure for Double Marker Test

During a double marker blood test screening, first, an ultrasound will be performed. Then, a blood test will be done to determine the levels of the two markers: Free Beta-hCG (BHB) and Free PAPP-A (PAPP-A). Administering this test is straightforward, as it only requires a blood sample from the expectant woman.

Additional steps include:

• Using a syringe to collect the blood specimen from the arteries.
• Applying an elastic band to the arms causes the blood vessels to swell.
• Once the arteries become visible, apply a special antiseptic to clean the targeted area.
• Carefully insert the needle, which may cause a pinprick sensation as it enters the blood artery. Before testing, samples are collected, preserved, and processed.

This is a straightforward procedure that typically takes only five to ten minutes to complete. Therefore, it is advisable to schedule a Dual Marker Test to better manage the condition.

Uses of Double Marker Test

To determine whether the foetus has any chromosomal abnormalities, a double marker test is utilised. The test is essential for identifying any neurological issues, such as Down syndrome or Edwards syndrome, in the foetus. The Double Marker Test, commonly known as Maternal Serum Screening, is highly recommended during the first trimester of pregnancy. It is one of the most important maternal screening tests conducted during pregnancy. The use of double marker tests is primarily to detect conditions like Down syndrome, also known as trisomies 21, 18, and 13, which can result in physical and mental challenges for the unborn child.

How to Prepare for the Double Marker Test?

There is no need for specialised preparation for the test; it is quite simple. However, it is essential that patients inform their physician of their current medications and any allergies they may have. Depending on this information, they may be advised to temporarily discontinue certain medications before the test. This test is non-fasting and can be administered at any time of day.

Values of Double Marker Test Results

The double marker test report can determine whether the baby is at low risk, moderate risk, or high risk for developing a chromosomal abnormality. A normal outcome is either a low-risk result or a screen-negative result. A double marker test negative indicates that the likelihood of the child having chromosomal abnormalities is unlikely. A double marker test positive indicates moderate or high risk, which may require further testing, such as non-invasive prenatal testing (NIPT), to confirm the diagnosis.

The normal hCG value in the Double Marker Test for pregnant women ranges from 25700 to 288000 mIU/ml across all age groups. The PAPP-A dual marker test normal range for pregnant women is 1 MoM (multiple of the median) across all age groups for females.

The double marker test results are typically classified into two distinct subcategories:

What are the Benefits of a Double Marker test?

The dual marker blood test has several advantages for parents, including:

• The double marker test not only provides parents with the information they need to make informed pregnancy decisions but also detects defects in the growing foetus.
• The Double Marker Test is non-invasive, posing no risk to both the expectant mother and the unborn child. In fact, it's a simple method for detecting certain chromosome abnormalities in the foetus during pregnancy.
• This process helps identify pregnancy-related risk factors and assesses whether the pregnancy might be harmful to the mother's health.
• The cost of the dual marker test is also affordable. It is a cost-effective method for detecting chromosomal abnormalities during pregnancy and is accessible to a wider group of women who may not have access to more expensive diagnostic testing.
• Some women find that knowing the results of a Double Marker Test provides them with peace of mind and helps them prepare for their baby's birth.

Conclusion

It is strongly advised to perform a double marker test to detect abnormalities early in pregnancy. While not mandatory, a dual marker test report can provide additional information that aids in pregnancy development and management.

FAQs

1. How accurate is a Double Marker Test? 

Ans. The double marker test in pregnancy is not diagnostic but rather predictive. It does not provide a definitive scientific analysis but indicates the probability of chromosomal anomalies.

2. Is the Double Marker Test compulsory? 

Ans. The double marker test isn't mandatory but is highly recommended, especially for expecting mothers over 35 with a high risk of chromosomal problems.

3. How long does the Double Marker Test take? 

Ans. The double marker test typically takes only five to ten minutes due to its simplicity.

4. Are there any risks associated with the Double Marker Test? 

Ans. The double marker test carries no risks. This blood test is routine and non-invasive.

Reference:
https://www.healthline.com/health/pregnancy/double-marker-test#what-it-is
https://www.metropolisindia.com/blog/disease/double-marker-pregnancy-test/
https://redcliffelabs.com/myhealth/lab-test/pregnancy-test/double-marker-test-during-pregnancy/