Double Marker Screening

Useful For 
Prenatal screening for Down syndrome and trisomy 18.
Method Description
The first-trimester screen for trisomy 21 and trisomy 18 includes pregnancy-associated plasma protein A (PAPP-A), total human chorionic gonadotropin (b-hCG), nuchal translucency (NT) measurement, and Crown-rump length (CRL).
Advisory Information
First-trimester screening is performed between 11 and 13 weeks of gestation. Analyte measurements are paired with ultrasonographic measurement of nuchal translucency (NT. A rise in NT is usually found in 21, 13, and 18 Trisomies and in 45, X fetuses. NT varies with fetal age and thus needs to be assessed in respect to gestational age.
Necessary Information
Approval to send specimen for first-trimester screening is required and may take up to 2 business days to complete.

Specimen Type
Collection Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Specimen Volume: 2-3 mL
Collection Instructions: Centrifuge and aliquot within 2 hours of collection

Additional Information:

  • Blood needs to be drawn between 10 weeks 0 days and 13 weeks 6 days, which corresponds to a crown-rump length (CRL) range of 31 to 80 mm. (Recent USG is mandatory)
  • Initial or repeat testing is determined in the laboratory at the time of report and will be reported accordingly.
  • In case of IVF Pregnancy, days in-vitro and transfer date are required (Note: If the ovum is donated, donor age must be provided)

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