2/18/2024 0 Comments Harmony test results online![]() reported a high accuracy of NIPT for the detection of trisomy 21, trisomy 18, and trisomy 13 in women at a high risk for fetal aneuploidy (sensitivities (95% confidence interval) from 95.8% (86.1 - 98.9%) to 99.7% (98.0 - 100%) specificities above 99% almost all studies had a high risk of bias). The quality of tests is expressed as sensitivity (percentage of affected fetuses that are correctly identified) and specificity (percentage of non-affected fetuses that are correctly identified). ![]() As NIPT is a screening test and not a diagnostic test, it only provides information about the possibility of having an affected fetus. To analyze the fetal genome, NIPT uses cell-free fetal DNA (cffDNA) that circulates in the maternal blood and is detectable in maternal plasma from 5 weeks of gestation. Examples in this background section will focus on trisomy 21, not only because it is the most frequent, but also because most expecting parents are familiar with it. The other syndromes that NIPT can screen for are aneuploidies of the sex chromosomes X or Y generally, these have less severe health consequences for the persons affected. Of children affected with trisomy 18 or 13 most die before birth or shortly after birth. Some individuals can live independently as adults, others need substantial support and care. The conditions caused by these aneuploidies vary considerably in severity and manifestations: Trisomy 21 is the most frequent aneuploidy in children that are born alive and causes mild to severe intellectual disability and several morphological features as well as possibly other medical conditions, such as heart disease. The available NIPTs usually screen for all of the following seven chromosomal aneuploidies or for a subset of them: Down syndrome (trisomy 21), Edward syndrome (trisomy 18), Patau syndrome (trisomy 13), Turner syndrome (45,X), Klinefelter syndrome (47,XXY), Triple X syndrome (47,XXX) and Jacobs syndrome (47,XYY). Since the early 2010s, genomics-based noninvasive prenatal tests (NIPT) based on a blood sample from the pregnant women are offered in antenatal care to expecting parents who have a risk for certain chromosomal anomalies.
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