What this test measures
This is the same first-trimester biochemical screen as the standard Dual Marker — free β-hCG and PAPP-A measured between 11+0 and 13+6 weeks — but specifically analysed on a Roche cobas / Elecsys immunoassay system. Risk calculation uses Roche-calibrated MoM (Multiple of the Median) databases, integrated with the NT measurement, CRL, maternal age, weight, ethnicity, and chorionicity to produce a personalised risk for trisomy 21, 18, and 13.
Different platforms (Roche, Perkin-Elmer DELFIA, Siemens Immulite) produce slightly different absolute hormone values for the same blood sample because their reagent calibrations differ. The MoM normalisation removes this platform difference for risk calculation — but obstetricians and foetal medicine specialists often prefer that all screening (NT + biochemistry) and any follow-up be on the same platform for consistency, which is why the platform is sometimes stated explicitly on the test order.
Why it matters
Many large Indian foetal medicine programmes (Apollo, Fortis Medical Research, NHL Medical) standardise on Roche cobas for prenatal screening because it integrates with their existing immunoassay workflow and has well-validated software (SsdwLab / FMF-licensed). For patients, the choice of platform makes essentially no difference to the clinical decision — the same risk thresholds (1 in 250 typically) apply, and the same diagnostic confirmatory tests are used.
The practical reason this test is listed separately on Indian price catalogues is billing/contract — labs price platform-specific assays differently. For a patient, this version is functionally interchangeable with any other first-trimester combined screen at the same laboratory.
How to prepare
No fasting required. Schedule the blood draw close to your NT scan (within 1–2 days). Bring your NT report (with CRL, NT measurement, chorionicity), LMP, IVF/IUI status, ethnicity, weight, and prior pregnancy history.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Free β-hCG (Roche) (ng/mL (or MoM))[1] | Median MoM = 1.0 (Roche-calibrated) | Low MoM (<0.4) associated with trisomy 18 and 13. | High MoM (>2.5) associated with trisomy 21. |
| PAPP-A (Roche) (mIU/L (or MoM)) | Median MoM = 1.0 (Roche-calibrated) | Low PAPP-A MoM (<0.4) — chromosomal risk + placental insufficiency risk (IUGR, pre-eclampsia). | High PAPP-A not typically associated with chromosomal abnormality. |
| Calculated risk | < 1 in 250 = low risk | — | ≥ 1 in 250 = high risk. Counselling + diagnostic test (NIPT, CVS, amniocentesis). |
Dual Marker — what changes with the platform
| Feature | Implication for patient |
|---|---|
| Roche cobas / Elecsys | Roche MoM database; reagent traceable to FMF-validated software |
| Perkin-Elmer DELFIA | Different MoM database — different absolute values, same risk threshold |
| Risk threshold | 1 in 250 (same across platforms) |
| Detection rate | 85–90% for Down syndrome (same) |
| Follow-up if high risk | NIPT or CVS / amniocentesis (same) |
Frequently asked questions
Why does the test mention Roche?
Roche cobas / Elecsys is the immunoassay platform some Indian labs use for first-trimester biochemistry. Listing the platform helps obstetricians keep all screening on the same system for consistency. Clinically, results are interchangeable with other validated platforms.
Is the Roche version more accurate than non-Roche?
No. All FMF-licensed platforms (Roche, Perkin-Elmer, Siemens) give equivalent detection rates (~85–90% for Down syndrome) when combined with NT scan. The platform mainly affects internal lab workflow.
When is the test done?
Between 11+0 and 13+6 weeks, paired with the NT ultrasound.
Do I need to fast?
No.
My doctor wants the Roche version specifically — why?
Likely because the rest of your pregnancy testing (NIPT, follow-up biochemistry, anomaly scan integration) is being done on the same platform. Internal consistency across reports reduces interpretation errors.
Does the risk number cutoff differ?
No. 1 in 250 (or whatever the lab's explicit cutoff is) applies across all FMF-validated platforms.
If I screen high risk, what is next?
Genetic counselling, followed by NIPT (cell-free foetal DNA, ~99% sensitive) or a diagnostic test (CVS at 11–13 weeks, amniocentesis at 15+ weeks).
Can the test be done for a twin pregnancy on Roche?
Yes — Roche software supports twin pregnancy risk calculation with chorionicity input. Specify "twin" when booking.
Related Pregnancy / Prenatal tests
Tests commonly ordered alongside DUAL MARKER ON ROCHE, or that help interpret an unexpected result.
Sources & references
- Fetal Medicine Foundation — Platform-Licensed Assays · accessed 2026-05-30T00:00:00.000Z
- ACOG — Screening for Fetal Chromosomal Abnormalities · accessed 2026-05-30T00:00:00.000Z
- NIH MedlinePlus — First Trimester Screening · accessed 2026-05-30T00:00:00.000Z
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