The Double Marker test, also known as the Double Marker screen, is a prenatal test conducted between 11-14 weeks of pregnancy. It’s a non-invasive screening test that measures two substances in the mother’s blood:
Markers:
1. Free beta-human chorionic gonadotropin (free β-hCG)
2. Pregnancy-associated plasma protein-A (PAPP-A)
Purpose:
The Double Marker test assesses the risk of:
1. Down syndrome (Trisomy 21)
2. Trisomy 18 (Edwards syndrome)
3. Trisomy 13 (Patau syndrome)
How it works:
1. Blood sample: A maternal blood sample is taken.
2. Analysis: The levels of free β-hCG and PAPP-A are measured.
3. Calculation: The results are calculated using a complex algorithm, considering factors like:
– Maternal age
– Gestational age
– Weight
– Ethnicity
4. Risk assessment: The test provides a probability score for each condition.
Interpretation:
Results are usually categorized as:
1. Low risk (<1:270): No further testing needed.
2. Borderline risk (1:270-1:1000): Further testing recommended.
3. High risk (>1:100): Diagnostic testing (e.g., amniocentesis or chorionic villus sampling) recommended.
Limitations:
1. False positives/negatives: The test is not 100% accurate.
2. Detection rate: 80-85% for Down syndrome, lower for other trisomies.
3. Not diagnostic: Only identifies increased risk, not confirmation.
Follow-up:
If the Double Marker test indicates increased risk, further diagnostic testing may be recommended to confirm or rule out the condition.
Additional notes:
1. The Double Marker test is often combined with ultrasound scans (e.g., nuchal translucency) for improved accuracy.
2. Some hospitals/clinics offer additional markers (e.g., Triple/Quad Marker tests).
3. Consult your healthcare provider for personalized guidance and counseling.
Do you have any specific questions or concerns about the Double Marker test?
