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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 ...
Other screening tests, such as the Quad test, can also have false positives and false negatives. Even when the Quad results are positive (or, to be more precise, when the Quad test yields a score that shows at least a 1 in 270 risk of abnormality), usually the pregnancy is normal, but additional diagnostic tests are offered.
Genetic counseling usually is offered when the screening test result is positive. [citation needed] If a woman is already getting a Quad test for Down Syndrome screening, then the AFP-marker that is part of this test provides the screen result for neural-tube and abdominal wall defects.
174 11576 Ensembl ENSG00000081051 ENSMUSG00000054932 UniProt P02771 P02772 RefSeq (mRNA) NM_001134 NM_001354717 NM_007423 RefSeq (protein) NP_001125 NP_001341646 NP_031449 Location (UCSC) Chr 4: 73.43 – 73.46 Mb Chr 5: 90.64 – 90.66 Mb PubMed search Wikidata View/Edit Human View/Edit Mouse Alpha-fetoprotein (AFP, α-fetoprotein ; also sometimes called alpha-1-fetoprotein, alpha ...
Screening for Down syndrome by a combination of maternal age and thickness of nuchal translucency in the fetus at 11–14 weeks of gestation was introduced in the 1990s. [7] This method identifies about 75% of affected fetuses while screening about 5% of pregnancies. Natural fetal loss after positive diagnosis at 12 weeks is about 30%. [6]
While the specificity and positive predictive value are poor, fetal fibronectin testing has excellent sensitivity (100%) and negative predictive value (100%). Therefore, a negative fFN test is a very strong indicator that preterm birth is not likely to occur within the next 7 days. [5]
A suppressor screen is used to identify suppressor mutations that alleviate or revert the phenotype of the original mutation, in a process defined as synthetic viability. [13] Suppressor mutations can be described as second mutations at a site on the chromosome distinct from the mutation under study, which suppress the phenotype of the original ...
In fact, post-test probability, as estimated from the likelihood ratio and pre-test probability, is generally more accurate than if estimated from the positive predictive value of the test, if the tested individual has a different pre-test probability than what is the prevalence of that condition in the population.