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The types of tests performed on the sample will be determined by the patient's indications for undergoing amniocentesis. Fluorescent in-situ hybridization (FISH) and quantitative fluorescence polymerase chain reaction (QF-PCR) are two tests commonly performed on uncultured cells after amniocentesis, with results available within two days. [1]
The most common abnormality the test can screen is trisomy 21 (Down syndrome).In addition to Down syndrome, the triple and quadruple screens assess risk for fetal trisomy 18 also known as Edwards syndrome, open neural tube defects, and may also detect an increased risk of Turner syndrome, triploidy, trisomy 16 mosaicism, fetal death, Smith–Lemli–Opitz syndrome, and steroid sulfatase ...
In fact, consider that Down syndrome affects about 1:400 pregnancies; if you screened 4000 pregnancies with a Quad test, there would probably be 10 Down syndrome pregnancies of which the Quad test, with its 80% sensitivity, would call 8 of them high-risk. The quad test would also tell 5% (~200) of the 3990 normal women that they are high-risk.
One method of performing a prenatal genetic test involves an amniocentesis, which removes a sample of fluid from the mother's amniotic sac 15 to 20 or more weeks into pregnancy. The fluid is then tested for chromosomal abnormalities such as Down syndrome (trisomy 21) and trisomy 18, which can result in neonatal or fetal death.
Testing Women, Testing the Fetus by Rayna Rapp is a book, published in 1999, about analysis of the social repercussions of prenatal genetic testing.Rapp combines the data she collected herself with historical context of amniocentesis and genetic counseling to argue that amniocentesis and those abortions following positive test results is a social decision as much as an individual one.
The resulting test report should specify the assay method and equipment used, and the report of a quantitative test should also provide a reference range for the test result. Many laboratories report reference ranges that are based on all other samples tested in that laboratory, necessarily including samples with abnormal AFP concentrations due ...
PUBS provides a means of rapid chromosome analysis and is useful when information cannot be obtained through amniocentesis, chorionic villus sampling, or ultrasound (or if the results of these tests were inconclusive); this test carries a significant risk of complication and is typically reserved for pregnancies determined to be at high risk ...
Fetal trisomy of chromosome 21 is the cause of Down's syndrome. This trisomy can be detected by analysis of cffDNA from maternal blood by massively parallel shotgun sequencing (MPSS). [61] Another technique is digital analysis of selected regions (DANSR). [61] Such tests show a sensitivity of about 99% and a specificity of more than 99.9%.