Serological Markers (Trisomy 21)

Medical Scope

Maternal serum collected at 14-17+6 weeks of amenorrhoea can be measured for 2 or 3 markers:

• Double test: free βhCG + AFP
• Triple test: free βhCG + AFP + non-conjugated oestriol

Down’s Syndrome risk assessment is calculated using the following markers:

• Woman’s date of birth
• Gestational age
• Other factors including weight, smoking…

If risk assessment is ≥ 1/250, amniocentesis and karyotyping is recommended. If AFP is ≥ 2.50 kU/L, an ultrasound examination is also recommended, notably to investigate the possibility of an abdominal wall or neural tube defect.
Finally, the results for these various markers may point to other foetal or obstetric abnormalities.

Techniques

Assays are carried out using an immunofluorimetric method on Perkin Elmer AutoDelfia machines, and the risk is calculated by Elipse/ LifeCycle software (CE Marking).

Research and Development

Further investigations for foetal and obstetric abnormalities other than trisomy 21, can be performed.
Following the publication of the French National Authority for Health (HAS) on the "Evaluation of trisomy 21 screening strategies" in June 2007, Biomnis awaits further directives from the French General Health Guidelines (Direction Générale de la Santé) concerning the performance of the test in the first trimester and its legal framework. In the meantime, we are closely following developments and actively participating in interdisciplinary meetings on the subject.