![]() ![]() PAPP-A is a 187-kDa protein comprised of 4 subunits: 2 PAPP-A subunits and 2 pro-major basic protein subunits. Increased fetal NT measurements can therefore serve as an indicator of an increased risk for Down syndrome and trisomy 18. While fetal NT measurements obtained by ultrasonography increase in normal pregnancies with advancing gestational age, Down syndrome and trisomy 18 fetuses have larger NT measurements than gestational age-matched normal fetuses. The NT measurement, an ultrasound marker, is obtained by measuring the fluid-filled space within the nuchal region (back of the neck) of the fetus. If results are positive, the patient is typically offered counseling and diagnostic testing. The information from both trimesters is combined and a report is issued. The blood specimen is tested for AFP, unconjugated estriol, human chorionic gonadotropin, and inhibin A. If the risk from the first trimester is below the established cutoff, an additional serum specimen is collected in the second trimester for SEQB / Sequential Maternal Screen, Part 2, Serum. For a stand-alone NTD-risk assessment, order MAFP1 / Alpha-Fetoprotein (AFP), Single Marker Screen, Maternal, Serum. When the part 1 screen is completed, NTD risk is not provided. In that event, the patient is typically offered counseling and diagnostic testing. If the result from part 1 indicates a risk for Down syndrome that is higher than the screen cutoff, the screen is completed, and a report is issued. The results of the ultrasound measurement and blood work, along with the maternal age and demographic information, are used to calculate trisomy 21 (Down syndrome) and trisomy 18 risk estimates. Along with the NT measurement, a maternal serum specimen is collected to measure pregnancy-associated plasma protein A (PAPP-A). ![]() Therefore, NT data is accepted only from NT-certified sonographers. The ultrasound measurement, referred to as the NT measurement, is difficult to perform accurately. This test involves an ultrasound and a blood draw. Sequential screening combines biochemical and ultrasound markers (nuchal translucency: NT) measured in both trimesters of the pregnancy. Sequential screening is a type of cross-trimester screening that has an improved detection rate as compared to either first- or second-trimester screening. Various options for maternal serum screening are available and include: first trimester, second trimester, and cross-trimester. Verification: It involves static analysis technique (review) done without executing code.Maternal serum screening is used to identify pregnancies that may have an increased risk for certain birth defects, such as trisomy 21 (Down syndrome), neural tube defects (NTD) and trisomy 18. The V-Model is often used in safety-critical systems, such as aerospace and defense systems, because of its emphasis on thorough testing and its ability to clearly define the steps involved in the software development process.Maintenance: In the maintenance phase, the software is maintained to ensure that it continues to meet the customer’s needs and expectations.Deployment: In the deployment phase, the software is deployed and put into use.Testing: In the testing phase, the software is tested to ensure that it meets the customer’s requirements and is of high quality.Implementation: In the implementation phase, the software is actually built based on the design. ![]()
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