A double marker test is a screening test performed during the first trimester of your pregnancy. The blood is screened with two serum markers to detect chromosomal anomalies in the fetus.
Every human cell has 22 pairs of autosomes and one pair of sex chromosomes where XX are the sex chromosomes in female fetuses and XY are the sex chromosomes in males. Chromosomal anomalies like trisomies are when an extra copy of a particular chromosome is seen. Double marker test screens for the following trisomies.
- Down Syndrome or Trisomy 21
- Edward’s Syndrome or Trisomy 18
- Patau’s Syndrome or Trisomy 13
In this Article
What is a double marker test?
Also known as maternal serum screening or dual marker test, the double marker blood test is a predictive non-invasive test to check the likelihood of chromosomal anomaly in the fetus.
Here, the blood levels of two serum markers are tested namely,
- Free beta-human chorionic gonadotropin (beta-hCG)
- Pregnancy-associated plasma protein (PAPP-A)
Hence, the name double marker test. Abnormal levels of hCG or PAPP-A can indicate the chances of a chromosomal abnormality in the fetus.
Why is a double marker test done?
Double marker tests are routinely-performed, first trimester tests in the following situations.
- Advanced maternal age – age of the pregnant mother above 35 years
- Couple with a family history of chromosomal or genetic defects
- Couple with a previous child with congenital or chromosomal defects
What to expect during a double marker test?
A double marker test is a regular blood test where a certain amount of blood is drawn and tested. This test requires no fasting and no special preparations.
Sometimes, a double marker test is used along with an NT scan (nuchal translucency – the ultrasound that examines the clear tissue at the back of the baby’s neck) can help give more accurate results.
However, these scans are screening tests that need confirmation with definitive diagnostic and invasive tests such as:
- Chorionic Villus Sampling (CVS) in the first trimester – Between week 11- week 13 of pregnancy
- Amniocentesis in the second trimester – Between week 15 to week 20 of pregnancyAlso read:- https://pregajunction.com/blog/anomaly-scan-in-pregnancy-what-is-it-the-test-results-cost-in-india/
Interpretation of results of a double marker test
The turnover time for a double marker test results is generally 5 to 7 days from the day of the test performed. For a double marker test, you are likely to get one of the following outcomes:
- “Low-Risk” or “Screen-Negative” indicates a normal range of hCG and PAPP-A for the tests and likelihood of the baby having a chromosomal defect. The normal range means,
- Beta hCG = 25700-288000 mIU/ml for women of all age groups
- PAPP-A = 1 MoM (multiples of median) for women across all age groups
- “High-Risk” or “Screen-Positive” indicate,
- High levels of free beta hCG – indicating the risk of trisomy 18 or 21.
- Low levels of PAPP-A – lower than the normal range of plasma protein – indicate the probability of Downs syndrome.
The cost of the double marker test is almost Rs.2,500/- and is subject to differ among the laboratories and cities.