A decree provides for the introduction of a non-invasive test, an alternative to amniocentesis, in routine detection of genetic diseases in utero.
Amniocentesis remains an anxiety-inducing examination for a pregnant woman. The risks of miscarriage and premature childbirth are not negligible. In recent years, a new test has made it possible to avoid a large part of amniocentesis which will give negative results: the examination of free circulating fetal DNA.
By a decree published in Official newspaper on May 7, the government formalized the intention to offer it as a routine soon, probably in 2017. “The prescription and performance conditions will be set by a decree of the Minister of Health, taken on the proposal of the Director General of the Biomedicine Agency, after the opinion of the National Agency for the Safety of Medicines and Health Products (ANSM) ”, specifies the decree.
A test already used
This text follows the positive scientific evaluation of the High Authority for Health (HAS). The institution will soon publish a second medico-economic part of its assessment, which will make it possible to set the conditions under which the test will be offered in French maternity hospitals.
In the meantime, the unreimbursed test is available around 400 euros, and the AP-HP has been offering it for free since the beginning of May in its Ile-de-France establishments. This technique, requiring only a blood sample, is both much more specific and more sensitive, that is to say that it produces very few false positives and false negatives.
DNA from the fetus to the mother
The new technique, already in place at Cochin Hospital for over a year, is based on a simple principle. There are two types of DNA circulating in the mother’s blood. That of the mother, of course, but also that of the fetus. By isolating the latter, it is now possible to perform sequencing and detect abnormalities in the number of chromosomes.It works for trisomy 21, but also for trisomies 18 and 13, which are rarer.
100% of Down’s syndrome detected
By approaching 100% of trisomies 21 detected, this blood test would prevent half of the amniocentesis, estimates Professor Jean-Michel Dupont, of the cytogenetics department of Cochin hospital (Paris), where the brand new automated platform top flow rate, intended for plasma DNA analysis, was installed.
“In cases where the test by analysis of circulating DNA turns out to be negative, we know that the residual risk is very low, which makes it possible to avoid recourse to this invasive procedure,” he explains.
Until now, the diagnosis has been based on a blood test, combined with an ultrasound. However, the commonly used serum marker test can only detect 70 to 80% of abnormalities, and has false positives. In these cases, pregnant women must undergo an amniocentesis – a sample of the amniotic fluid – or a biopsy of part of the placenta, which is then unnecessary and increases the risks associated with the pregnancy.
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