Significance of Double Marker Test

Healthcare Jul-05-2023 0

For every woman, pregnancy might be a miraculous moment. Throughout pregnancy, it's essential to see a gynecologist to ensure both the mother and fetal health. There are several tests available to examine your baby's growth status, nutrient levels, and potential genetic conditions. One of them is biochemical screening called as Double Marker Test.

The purpose of Double Marker Test during pregnancy is to determine the risk of trisomy (chromosome abnormalities) in the fetus. It is carried out twice: in the I and II trimesters, its results are evaluated exclusively by the doctor after studying the patient's history. Deviations from the norm of quantitative values of specific markers determined during screening are not sufficient for making a diagnosis but are considered the basis for a more in-depth medical examination.

What is a double marker test?

The double marker test (dual marker) is a non-invasive screening done during the first trimester to detect aneuploidy (presence of an abnormal number of chromosomes) pregnancies. It plays an important role in determining the likelihood of having a child with neurological diseases such as Down's syndrome (trisomy 21), Edward's syndrome (trisomy 18) and Patau's syndrome (trisomy 13). This is usually done between 10 and 14 weeks of pregnancy.

Why is the double marker test done?

Pregnant women who fall into a certain risk category may need to have this double marker test in the first trimester. Risk factors include:

• Age over 35
• The previous child was born with any chromosomal abnormality
• Family history of genetic diseases
• IVF pregnancy
• History of insulin-dependent type 1 diabetes
• History of medication consumption, such as antiepileptic drugs, and exposure to severe fever
• It is offered to all pregnant mothers everywhere but is not a mandatory test.

Benefits of the double marker test:

• He has enough time to decide on additional tests if they detect a chromosomal abnormality in the fetus.
• The results are quite accurate.
• You can go for an early termination, which will have fewer complications.
• In addition, it can help mark pregnancy, which can lead to preeclampsia, separation of the placenta, and fetal growth retardation. Thus, an early opportunity to change these conditions is offered.
Disadvantages of the double marker test:
• The dependency of obtaining accurate results for the dual marker test is a major factor in the skill set of the clinician and the equipment used to perform the treatment.
• At the same time, the costs of these tests are quite expensive. Therefore, not everyone can pass the test. Therefore, doctors only recommend these tests when they think it's important.
• Due to high cost and equipment requirements, these tests are not available in all cities across the country.

How Can One Get Ready For a double marker test?

The marker test is extremely straightforward and can be performed similarly to a routine blood test. It is not necessary to alter one's way of living before the test. Additionally, since the test is a non-fasting type, unless otherwise instructed, one can usually eat and drink before the appointment.

The doctor should be informed of any pre-existing allergies or medicines that could cause a problem, though. The test's straightforwardness is demonstrated by the way it is conducted, which begins with an ultrasound examination. A carer collects the blood sample after the NT-Scan, which is then examined. Overall, this exam has no unique prerequisites.

How is the double marker test performed?

The dual marker test analyses two markers in the mother's blood and is therefore named as such. It is properly called a combined test because it combines an occipital translucency (NT) scan with these two markers, which measure fluid behind the fetal cervix to detect Down syndrome.

Two markers:

• Free beta-hCG (human chorionic gonadotropin): High levels indicate a risk of Down's syndrome, while low levels indicate Edward's syndrome.
• PAPP-A (pregnancy-associated plasma protein): Low levels indicate a risk of Down syndrome.
• The result is a low, medium or high probability of the disease.
• If the result is "low", it means that there is a 98-99% chance that the disorder is not present.
• When the results are "moderate to high," additional confirmation is needed with an amniocentesis (examination of the baby's cells removed from the fluid around the baby). Amniocentesis is invasive because it involves access to this fluid through a needle inserted into the mother's womb and is associated with the possibility of miscarriage.

NIPT (Non-Invasive Perinatal Testing) is now available with comparable sensitivity to amniocentesis. In this test, the mother's blood is taken and the baby's extracellular DNA is examined.

Norm and interpretation of results

To evaluate the results of a double test, it is necessary to take into account not only the indicators of biochemical analysis, but also the results of an ultrasound scan.

Gestational age	PAPP-A	β-hCG
9-10 weeks	0.32 - 2.42	20000 ≥ - ≤ 95000 mU / ml
11-12 weeks	0.79 - 4.76	20000 ≥ - ≤ 90000 mU / ml
12-13 weeks	1.03 - 6.01	15000 ≥ - ≤ 60000 mU / ml
13-14 weeks	1.47 ≥ - ≤ 8.54

The results can be considered normal if the indicators do not deviate by more than 0.5-2 MoMa (the ratio of the actual data and the average value) in one direction or another.

A strong decrease in β-hCG is a sign of Edwards syndrome, an abnormal increase is Down syndrome, if multiple pregnancy is not established. A decrease in the concentration of PAPP-A protein makes it possible to suspect pathologies of chromosomes 18 and 21.

Abnormal test findings - now what?

If the level of beta-hCG is higher than normal, this is a positive marker of Down syndrome. Combined with a low PAPP-A value, this is considered a positive dual marker and you may need additional tests to confirm the diagnosis.
Further tests will be invasive, such as amniocentesis and chorionic villus sampling (CVS), and will check for fetal cells present in the amniotic fluid.

What is the cost of the test?

The cost of a dual market test can vary by city and even by hospital. The bottom end of the dough can cost as little as Rs. 1000 and on a higher side can go up even to Rs. 5000 or so. In such a case, the average price in many cities tends to fluctuate around Rs. 2500 or so.

Conclusion:

When a woman is pregnant, only thing she ensures is that her baby turns out to be healthy , free from any disorders and eventually leads a normal life. To ensure this, the most important thing will be choosing the right diet, the right lifestyle choices and the right efforts to keep self and baby safe.

The double marker test is a prenatal test performed as a screening tool to predict the possibility of chromosomal abnormalities, especially Down syndrome in a baby. This test has become available in recent years as a result of the analysis of collected and studied massive data.

A double marker test is highly recommended during pregnancy, but keep in mind that the findings only predict the overall risks, if any.

The benefits of this test outweigh its expense as it provides information on the disorder's risk. To determine whether additional tests are essential, it is necessary to speak with a qualified healthcare provider and genetics expert.

- Compiled by Dr. Rakesh Kumavat - Team Proceed Fit

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