- For Whom?
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PrenatalScreenis suggested in the following cases:
• Personal/familial anamnesis of hereditary genetic diseases
• For expectant mothers wanting to reduce the risk of a genetic disease in the fetus
• For natural pregnancies as well as medically assisted procreation procedures (MAP)
• For couples using heterologus artificial insemination procedures - What is diagnosed?
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PrenatalScreencan diagnose more than 1,000 genetic diseases such as Hereditary Deafness, Cystic Fibrosis, Sickle Cell Anaemia, Thalassaemia, Spinal Muscular Atrophy. The 744 genes investigated were selected:
- according to the percentage of diseases caused by mutation to such genes occurring in the population
- the severity of the clinical phenotype at birthin accordance with the indications of the American College of Medical Genetics (ACMG)(Grody et al., Genet Med 2013:15:482–483).
PrenatalScreen®
A genetic screening test which examines more than 1,000 genetic diseases in the fetus
Procedure
The diagnostic test PrenatalScreenis performed on fetal DNA available in amniotic fluid via amniocentisis or in chorionic villi through chorionic villus sampling.
On Amniotic Fluid:
An ultrasound-guided transabdominal aspiration of 15-20 ml of amniotic fluid, between the 15th and the 18th week of pregnancy is performed. The centrifugation of the amniotic fluid is done to obtain fetal cells from which DNA is extracted.
Or else
On Chorionic Villi:
An ultrasound-guided transabdominal collection of around 20 mg of chorionic villi between the 11th and the 13th week of pregnancy is performed. The collected material is washed and observed under the microscope to separate the maternal tissue from the fetal tissue. Then DNA is extracted.
The DNA is then amplified through PCR and using ILLUMINA sequencing through a state-of-the-art technological process called massive parallel sequencing (MPS), which uses Next Generation Sequencing (NGS) (exons and adjacent intrionic regions, ± 5 nucleotides). The resulting genetic sequences are analyzed via an advanced bioinformatics analysis, to check the presence of potential mutations in the examined genes.
If PrenatalScreenhas a negative result
No mutations:
this result shows that the test has not detected any mutations in the examined genes. Such a result significantly reduces the probability that the fetus carries the examined genetic diseases, although no guarantee may be given that the fetus is actually healthy.
If PrenatalScreenhas a positive result
Presence of one or more mutations:
this result shows that the test detected one or more mutations in one or more genes. Mutations detectable through the PrenatalScreentest may be classified under the following prognosis categories:
A) with known prognostic outcome;
B) with benign outcome since they may be detected in healthy individuals and are not associated with any pathological outcome;
C) with uncertain outcome since they are not yet known or classified by the medical and scientific community.
Accuracy and testing limit
Present DNA sequencing techniques are more than 99% accurate. One must remember that PrenatalScreenevaluates only the genetic diseases and the genes listed in Table. The test does not evaluate other genetic diseases or genes not listed.
A “NEGATIVE” result - (no mutations result for the examined genes) does not exclude the possibility that mutations are present in the fetus in a region of the genome that was not explored during the examination. In some cases, the results of a genetic analysis can show a variation or a DNA mutation with a clinically uncertain result not yet known or classified by the medical and scientific community. The interpretation of genetic variations is based on the most recent knowledge available at the time of the analysis. Such an interpretation could change in the future when new scientific and medical information regarding the genome structure and could influence the evalution of these variations.
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