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. 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. Centrifuge and aliquot serum into plastic vial within 2 hours of collection. The ultrasound and blood draw must be completed within a gestational window of 10 weeks, 0 days and 13 weeks, 6 days, which corresponds to a crown-rump length range of 31 to 80 mm.Ģ. Complete the NT/CRL Data for First Trimester/Sequential Maternal Screening.ġ. See Maternal Screening: Sonographer Approval Process in Special Instructions. Do not send specimen to Mayo Clinic Laboratories if the sonographer is not NT-certified or before completing the application process. Nuchal translucency (NT) measurements are only accepted from NT-certified sonographers. Sequential maternal screening is a 2-part test that includes a first-trimester sample (SEQA / Sequential Maternal Screening, Part 1, Serum) and a second-trimester sample (SEQB / Sequential Maternal Screening, Part 2, Serum).Īpproval to send specimen for first-trimester screening is required and may take up to 5 business days to complete. If a stand-alone neural tube defect risk assessment is desired, order MAFP1 / Alpha-Fetoprotein (AFP), Single Marker Screen, Maternal, Serum. If collecting a second-trimester specimen is expected to be difficult, order first-trimester screening instead (see 1STT1 / First Trimester Maternal Screen, Serum). When part 1 is negative, part 2 must be completed in order to receive an interpretable result.
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