Double Marker

What is Dual Marker Test?
Dual marker test is a first trimester screening test advised to all pregnant women, for assessing the risk of certain genetic abnormalities in the fetus. It can be conducted between the 9th-13th week of pregnancy, but the ideal sampling time is between 11-13th week. The term “Dual Marker” means two markers are tested -Free beta human chorionic gonadotropin ( fβ-HCG ) & Pregnancy-Associated Plasma Protein (PAPP-A ). It helps in evaluating the risk of a fetus developing Trisomy 21 (Down syndrome) and Trisomy 13/18 syndrome. As these genetic conditions lead to mental retardation and other medical illnesses which might impact the vital organs of the fetus, it is extremely crucial for all pregnant women to undergo this investigation.

Dual Marker is a screening test, not a diagnostic test. This test is based on a predictive and statistical approach, further testing is always needed to confirm a diagnosis.

*The accuracy of the results is subjective to the information provided in the screening form(Annexure – CR 02) and this information is mandatory for combined risk assessment

* For combined risk assessment, it is always advisable to get tested in 11-13 weeks of pregnancy.

What does Dual Marker Test Measure?
This test measures the levels of b-hCG and PAPP-A in blood with the ultrasound test. b-hCG is a hormone which is produced by the cells in the developing placenta during pregnancy. The levels of b-hCG increases in early pregnancy. The role of b-hCG in early pregnancy is to maintain the function of corpus luteum (the hormone-secreting structure that develops in an ovary). During the first three weeks production of b-hCG increases reaching to peak levels at 10th week (from the last menstrual cycle). After that, the levels of b-hCG start to fall to negligible within a few weeks after delivery.

PAPP-A is secreted by the placenta and its levels increase with duration of pregnancy. Variety of tissues express PAPP-A at very lower levels. Plaques which are not stable in coronary arteries also express PAPP-A in high levels.

Dual marker test is done along with Nuchal Translucency test to confirm the diagnosis of any genetic abnormality.

Nuchal Translucency (NT) is a measurement of the fluid beneath the skin along the back of the baby’s neck. NT is measured by ultrasonography.