T21 screening – Pre-eclampsia – Fœtal biochemistry

Also related to pregnancy, further pathophysiological research on pre-eclampsia (PE) has led to the development of angiogenic and antiangiogenic factor analyses that can be used for predictive and screening tests.

• T21: assay on maternal serum markers
• NIPT T21 : Non-invasive prenatal testing for trisomy 21
• Pre-eclampsia screening and predictive test
• Foetal biochemistry  

T21 : assay on maternal serum markers

• 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).

NIPT T21 : Non-invasive prenatal testing of trisomy 21

In fact, aside from its excellent performances in terms of sensitivity and specificity, the introduction of NIPT is expected to reduce significantly the number of invasive procedures (sampling of chorionic villi and amniotic fluid) performed on women at risk and, therefore, the number of associated foetal deaths (0.5-1%).

There are actually two methods available for NIPT: a targeted method (on chromosomes 13, 18, and 21) and a global pangenomic method based on massive DNA sequencing (Massively-Parallel Sequencing or MPS). Eurofins Biomnis uses the MPS technology (Verifi®) on a HiSeq™ 2500 sequencer from Illumina, which currently presents the best screening performance for the predominant aneuploidies using a non-invasive technique.

NIPT can be performed starting on Week 12 of amenorrhoea. In accordance with the recommendations on the best prenatal diagnosis practice (decree no. 2014-32 of 14 January 2014), the implementation of this genetic test requires clear information and the patient’s consent.

Our pathologists are members of the ACLF (Association des Cytogénéticiens de Langue Française; French Cytogenetics Association) and URPHE (Union Régionale pour la Prévention des Handicaps de l’Enfant; Regional Association for the Prevention of Child Disabilities).

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Pre-eclampsia screening and predictive test

Pre-eclampsia screening

The advantage of early detection of pre-eclampsia is the possibility to initiate low-dose aspirin therapy before Week 16 of amenorrhoea and/or to implement close monitoring of the pregnancy. This screening, during the 1st trimester of pregnancy, combines PAPP-A and PIGF assays (Delfia Xpress™ system, Perkin Elmer). The risk of PE is calculated by the software (Predictor™) using the levels of PAPP-A and PIGF, biophysical measurements (blood pressure, uterine artery Doppler scan), demographic information on the patient (BMI, geographic origin, smoker/non-smoker, etc.), her medical history (number of prior viable pregnancies, PE, and high blood pressure), and the ongoing pregnancy (gestational age, the date of the ultrasound, and the CRL).

Pre-eclampsia predictive test

This test is for symptomatic patients beyond Week 24 of amenorrhea. The use of the sFlt-1/PlGF ratio allows the occurrence of pre-eclampsia (PE) to be predicted within 1 to 4 weeks. This ratio can help the doctor decide whether to keep the patient at home to or bring them in to the hospital, as well as adjust treatment and anticipate foetal-maternal complications.

The placental growth factor (PIGF) and sFlt-1 antiangiogenic factor are biomarkers that are closely linked to PE. An imbalance in the concentration of these two markers occurs several weeks before the first clinical signs of pre-eclampsia. As such, an increased sFlt-1/PlGF ratio is associated with a risk of pre-eclampsia.

Our biologists are members of the Groupe de Biologie Spécialisée de la Société Française de Médecine Nucléaire (Specialised Biology Group of the French Society of Nuclear Medicine), SFBC (Société Française de Biologie Clinique; French Society of Clinical Biology), and ELAS (European Ligand Assays Society).

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Foetal biochemistry

This laboratory assays alpha-fetoprotein and tests for acetylcholinesterase in amniotic fluid.

Acetylcholinesterase is an enzyme expressed exclusively in the nervous system and the neuromuscular junction. This enzyme is only detected in amniotic fluid if the foetus presents a defective closure of the neural tube.

Eurofins Biomnis possesses the mandatory certifications issued by the ARS (Agences Régionales de Santé; French Regional Health Agencies), as well as the technical means and expertise to perform and interpret these different tests.