After validating the performance of new genetic screening tests for trisomy 21, known as “free circulating DNA tests for trisomy 21 in maternal blood”, the High Authority for Health (HAS) today defined their place and conditions of use in the screening procedure.
“The objective is to give pregnant women or couples the most reliable information possible on the risk of fetal trisomy 21 while limiting the use of invasive examinations necessary to confirm the diagnosis” declares the High Authority in a press release.
Trisomy 21 affects 27 out of 10,000 pregnancies
Trisomy 21 is a chromosomal abnormality characterized by an extra chromosome 21. It is observed on average in 27 out of 10,000 pregnancies and its frequency increases with maternal age. Until now, the screening test was carried out by amniocentesis, by removing with a long needle, part of the amniotic fluid. An examination that presents a risk of fetal loss, low but not zero.
But of new screening tests have been developed which make it possible to search for an overrepresentation of chromosome 21 in the free DNA circulating in the maternal blood.
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Until now, the place of these new tests having not been evaluated in France, they are neither included in the methods of prenatal screening, nor covered by health insurance. Today, HAS recommends offering free circulating T21 DNA testing after combined 1st trimester screening (which combines nuchal translucency measurement with ultrasound and serum marker assay), to women whose level The estimated risk is between 1 in 1000 and 1 in 51. However, the place of the fetal karyotype remains unchanged: only this examination can make a diagnosis.
For women whose risk is greater than or equal to 1 in 50, HAS maintains its recommendation to offer them a fetal karyotype from the outset, but including the possibility for those who wish to do so first. a DNA test.
“This integration of a DNA test in the screening for fetal trisomy 21 will make it possible to refine the risk assessment and thus better target the women to whom a fetal karyotype will be offered. Compared to 2009, the new screening strategy will improve the trisomy 21 detection rate while reducing the number of unnecessary invasive examinations” emphasizes the HAS.
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Trisomy 21: the most common congenital anomaly
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