The prenatal tests comparing

The tests of prenatal screening in the first trimester of pregnancy, such as the measurement of nuchal translucency combined with the two biochemical markers, free-βHCG and PAPP-A, are non-invasive prenatal testing, but have a false positive rate of up to 5% and They do not detect correctly up to 30% of cases of trisomy 21.

These tests can, in fact, bring a positive for fetal trisomy although in fact we are in the presence of a pregnancy with a healthy fetus (false positive) or may bring a negative for fetal trisomy, while in reality we are dealing with pregnancy a fetus with fetal trisomy (false negative).

The prenatal screening tests, such as amniocentesis and chorionic villus sampling, while having a screening reliability of over 99% for all trisomies and fetal aneuploidy, are highly invasive and have a potential risk to the health of the mother and fetus (up to cause the ' abortion).

The following table compares the advantages and the limitations of current prenatal screening test non-invasive and invasive with latest-generation test performed on maternal blood.

TEST TYPE OF SAMPLE ADVANTAGES LIMITI
Screening tests of the 1st trimester of pregnancy
based on the combination of biochemical markers and ultrasound data (PAPP -A , free β - hCG and NT)
Non-invasive:
- Maternal Blood Sampling
- Data sonographic
- Secure: extremely limited risk for the mother and the child
- Reasonable costs
Indirect tests on a statistical basis
Multiple visits to screen
Up to 5% of false positives
Up to 30% of false negatives
Amniocentesis - chorionic villus sampling
(Chromosome analysis)
Invasive:
- Removal of amniotic fluid
- Withdrawal chorionic villi
- High screening acccuratezza
- Possibility of cytogenetic or molecular testing
Risk of miscarriage ' (0.5 - 1 % )
Possibility 'of complications for the mother
High cost for the patient and for the health system
Non-invasive test using fetal DNA
First-generation test (shotgun sequencing)
Non invasive:
- Blood sample
- Accurate
- Sicure
High cost for the patient
Limited to the detection of fetal trisomy sun
Harmony Prenatal Test
Direct test DNA
Non invasive:
- Maternal Blood Sampling
- Accuracy > 99 % for Down Syndrome
- Sicure
- Efficient and economical
- Customized quantitative results