What is a Quadruple Marker Test?
The Quadruple Marker Test (also called the Quad Screen) is an advanced second trimester prenatal blood test performed between 15 and 20 weeks of pregnancy. It is an enhanced version of the Triple Marker test, adding a fourth marker — Inhibin-A — to significantly improve the detection rate for Down Syndrome. By measuring four biochemical substances in the mother's blood and combining them with maternal age, gestational age and body weight, the Quad Screen generates a comprehensive risk profile for chromosomal abnormalities and neural tube defects in the developing baby.
- Your latest ultrasound (USG) report confirming gestational age and fetal measurements
- Your gynaecologist's prescription or referral
- Your exact date of birth and current body weight
- Your LMP (Last Menstrual Period) date
- Information on whether you are diabetic (diabetes affects marker levels)
The Four Markers Explained
The Quad Screen measures four placental and fetal biochemical markers:
- AFP (Alpha-Fetoprotein) — produced by the baby's liver. High AFP indicates risk of open neural tube defects (Spina Bifida, Anencephaly). Low AFP suggests risk of Down Syndrome or Edwards Syndrome.
- HCG (Human Chorionic Gonadotropin) — produced by the placenta. High HCG is associated with Down Syndrome. Low HCG suggests Edwards Syndrome (Trisomy 18).
- uE3 (Unconjugated Estriol) — produced jointly by the placenta and fetal adrenal glands. Low uE3 indicates risk of Down Syndrome and Edwards Syndrome.
- Inhibin-A — the key addition in the Quad Screen. A protein produced by the placenta that is significantly elevated (above 2.0 MoM) in Down Syndrome pregnancies. Adding Inhibin-A raises the Down Syndrome detection rate from approximately 70–75% (Triple Marker) to approximately 80–85%.
Why Inhibin-A Makes the Quad Screen More Powerful
- In Down Syndrome pregnancies, Inhibin-A is typically elevated to about 2.0 MoM — in the opposite direction to AFP and uE3 which are low.
- This additional data point significantly improves the statistical discrimination between Down Syndrome and normal pregnancies, raising the detection rate by approximately 5–10 percentage points.
- The false positive rate (high-risk result in a normal pregnancy) is reduced compared to the Triple Marker alone.
- Elevated Inhibin-A alongside elevated HCG with low AFP and uE3 creates the strongest biochemical signature for Down Syndrome in the second trimester.
- Inhibin-A also has independent clinical value — elevated levels are associated with increased risk of pre-eclampsia and placental dysfunction.
Quadruple Marker Pattern by Condition
| Condition | AFP | HCG | uE3 | Inhibin-A |
|---|---|---|---|---|
| Down Syndrome (Trisomy 21) | Low | High | Low | High |
| Edwards Syndrome (Trisomy 18) | Low | Low | Low | Normal/Low |
| Open Neural Tube Defect | Very High | Normal | Normal | Normal |
| Normal Pregnancy | Normal | Normal | Normal | Normal |
All values are expressed as MoM (Multiples of the Median). The risk calculation software combines all four MoM values with maternal age, weight, gestational age and ethnicity to generate a final risk ratio for each condition.
Quad Screen vs Triple Marker vs Dual Marker vs NIPT
| Test | Timing | Markers | Down Syndrome Detection | Neural Tube Defect |
|---|---|---|---|---|
| Dual Marker + NT | 11–14 weeks | Free Beta-HCG, PAPP-A + NT scan | ~85–90% | No |
| Triple Marker | 15–20 weeks | AFP, HCG, uE3 | ~70–75% | Yes (AFP) |
| Quad Marker | 15–20 weeks | AFP, HCG, uE3, Inhibin-A | ~80–85% | Yes (AFP) |
| NIPT | 10+ weeks | Cell-free fetal DNA | >99% | No (NTD not screened) |
| Amniocentesis | 15–20 weeks | Fetal karyotype | 100% (diagnostic) | 100% (diagnostic) |
When is the Quadruple Marker Recommended?
The Quad Screen is recommended for:
- Women who missed the first trimester Dual Marker window (11–14 weeks)
- Women who want the most accurate second trimester biochemical screen available
- Women of Advanced Maternal Age (35 and above)
- Women with a high-risk Triple Marker result needing a more comprehensive screen
- Women with a family history of Down Syndrome, neural tube defects or other chromosomal conditions
- Women with IVF pregnancies or a history of chromosomally abnormal pregnancies
- When NIPT is not affordable and maximum second trimester screen accuracy is desired
Quadruple Marker Test Price in Kolkata
No fasting required | USG report & prescription mandatory | 15–20 weeks gestational window (ideal: 16–18 weeks) | Results in 24–48 hours
Tests in the Prenatal Screening Pathway
- Dual Marker + NT (11–14 weeks) — first trimester combined screen; most accurate first line option
- Quadruple Marker (15–20 weeks) — this test; best available second trimester biochemical screen
- Level 2 Anomaly Scan (18–20 weeks) — detailed structural fetal survey; ordered alongside Quad Marker
- NIPT (10+ weeks) — most accurate non-invasive option; can be ordered instead of or alongside Quad Marker
- Amniocentesis (15–20 weeks) — definitive diagnostic test when Quad Marker is high-risk
- Fetal Echocardiography — heart scan when Down Syndrome risk is elevated (cardiac defects are common in Trisomy 21)
Home Collection for Quadruple Marker Test in Kolkata
Apollo Diagnostics provides home blood sample collection for the Quadruple Marker test across Nagerbazar, Dum Dum, South Dum Dum and surrounding North and Central Kolkata areas. Please ensure your USG report confirming gestational age and your gynaecologist's prescription are ready at the time of home collection — both are mandatory for accurate risk calculation.
- Home collection available: 7:00 AM – 2:30 PM Daily
- No fasting required
- USG report and prescription mandatory at time of collection
- Must be within 15–20 weeks gestation (ideal 16–18 weeks)
- Results in 24–48 hours
- Free home collection on orders above ₹2,000
→ Apollo Diagnostics Nagerbazar → Full List of Individual Tests → Book Home Collection → Full Body Checkup Packages
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