- What is a double marker test?
- Why is the double marker test done?
- Do you need to prepare for the test?
- How is the double marker test done?
- What are the average test values of biochemical markers?
- What if the test results are not within the normal range?
- Advantages of a double marker test
- Drawbacks of the double marker test
- What is the cost of the test?
Among the many prenatal tests done on pregnant women, some are necessary while others are recommended only if the doctor thinks they are important. One such test that is suggested upon detecting any problem is a double marker test. To learn about why, when and how this test is performed, read this MomJunction post.
What Is The Double Marker Test?
A double marker (dual marker) test is a non-invasive screening done during the first-trimester to detect aneuploidy (presence of abnormal chromosome number) pregnancies. It plays a prominent role in identifying the likeliness of having a baby with neurological conditions, such as Down’s syndrome (trisomy 21), Edward’s syndrome (trisomy 18), and Patau’s syndrome (trisomy 13). It is usually done between the 10th and 14th weeks of pregnancy (1).
Why Is The Double Marker Test Done?
Pregnant women who fall under a particular risk category may have to undergo this double marker test in their first trimester. The risk factors include:
- Age above 35 years
- Previous baby born with any chromosomal abnormality
- A family history of genetic conditions
- IVF pregnancy
- History of insulin-dependent type-1 diabetes
Do You Need To Prepare For The Test?
The Double Marker Test is a simple blood test that does not need any specific preparations. Let your doctor know if you are on any medications since you might be advised to refrain from them for sometime before the test.
How Is The Double Marker Test Done?
The Double Marker Test is primarily dependent on the Nuchal Translucency (NT) scan that measures the fluid behind the fetal neck to screen for Down syndrome. Depending on the NT measurements, blood test sampling is carried to check for two markers.
- Free beta hCG (human chorionic gonadotrophin) – High levels show the risk of Down’s syndrome, and low levels indicate Edward’s syndrome.
- PAPP-A (Pregnancy-associated plasma protein) – Low levels show the risk of Down’s syndrome (2).
If the result is positive, there is a chance to terminate the pregnancy in the early stages itself without any complications.
What Are The Normal Test Values Of Biochemical Markers?
What If The Test Results Are Not Within The Normal Range?
If the beta hCG levels are more than the normal range, it is a positive marker for Down syndrome. If coupled with low PAPP-A value, it is taken as a positive double marker, and you may need additional tests to confirm the diagnosis.
Further tests would be invasive, such as amniocentesis and chorionic villus sampling (CVS), and would test the fetal cells present in the amniotic fluid (5).
Advantages Of The Double Marker Test
- It offers enough time to decide on additional tests if they detect a chromosomal abnormality in the fetus.
- The results are reasonably accurate.
- You can go for early termination that holds fewer complications.
Drawbacks Of The Double Marker Test
- It is highly expensive and not everyone can afford it.
- It is not available in every city.
What Is The Cost Of The Test?
The cost of the Double Marker Test varies across cities and hospitals. It might range between Rs. 1000 and Rs. 5000 based on the location, quality, and availability.
Every pregnancy screening test has its significance. However, you should be discussing all the pros and cons with your doctor before going for any test. If the results are positive, wait for your doctor’s confirmation before worrying. Sometimes positive screening results may become negative during final review and confirmation.
Have you got the Double market Test done earlier in your pregnancy? Write to us about your experiences in the below comment section.
2. Asma Khali &, Pranav Pandya; Screening for Down syndrome; The Journal of Obstetrics and Gynecology of India (2006)
3. Hsiao-Ching Yee et al.; Method for determining hCG levels in fluid samples; AmeriTek USA Inc; Google Patents
4. Low PAPP-A; Hampshire Hospitals (2016)
5. David S. Newberger; Down Syndrome: Prenatal Risk Assessment and Diagnosis; American Family Physician