The decree of 23 June 2009 (official journal of July 2009) defines the good practice guidelines for the screening and prenatal diagnosis of trisomy 21. These guidelines offer three options of screening protocols using maternal serum markers during the 1st or 2nd trimester of the pregnancy.
- a screening test combining 1st trimester ultrasound measurements (crown-rump length or CRL, nuchal translucency or NT, and the date of the ultrasound) and 1st trimester maternal serum markers (the Pregnancy-Associated Plasma Protein-A or PAPP-A and the hCGß subunit). The samples must be collected between Week 11 Day 0 of amenorrhoea and Week 13 Day 6 of amenorrhoea (corresponding to a CRL of 45-84 mm).
- a sequentially integrated screening test analysed during the 2nd trimester based on the 1st trimester ultrasound measurements (same as above) and 2nd trimester maternal serum markers (total hCG or the hCGß subunit, and AFP +/- estriol). The samples must be collected between Week 14 Day 0 of amenorrhoea and Week 17 Day 6 of amenorrhoea.
- a screening test based only on 2nd trimester maternal serum markers.
The serum markers are assayed using an immunofluorometric technique on an AutoDelfia™ automatic immunoassay system (Perkin Elmer), and the risks are calculated using the LifeCycle software (CE marking).
Our pathologists are members of the ABA (Association des Biologistes Agréés pour le Dépistage Sérique Maternel de la Trisomie 21 Fœtale; Certified Biologists Association for the Maternal Serum Screening of Fetal Trisomy 21).