for Down syndrome

Sequential Screen | Fß

NTD Labs' Sequential Screen | Fß test reliably assesses a mother's risk for having a baby with Down syndrome, trisomy 18, trisomy 13 and open neural tube defects (ONTDs) during the first and second trimesters of pregnancy. Performed between 11 weeks, 1 day and 13 weeks, 6 days, and then again between 15 weeks and 21 weeks, 6 days gestation, the Sequential Screen | Fß uses data from 2 blood tests (biochemistry) and an ultrasound examination (biophysical) which yield two risk assessments that physicians may present to their patients during the first trimester and the second trimester.

Part 1 of the Sequential Screen | Fß

A maternal dried blood spot sample is analyzed for two biochemical markers in the first trimester: free beta human chorionic gonadotropin (free beta hCG) and pregnancy associated plasma protein-A (PAPP-A). Blood specimens are collected one of two ways, through a simple finger stick method, or with venipuncture. The venous blood is immediately spotted onto a dried blood spot card provided by NTD Labs using a Diff-Safe device or the blood is spotted directly from the finger.

The ultrasound examination in the first trimester confirms the fetus' gestational age and measures the nuchal translucency (NT), or the fluid accumulation behind the fetus' neck. These combined biochemical and biophysical markers yield the most sensitive screening results possible at the earliest point during the pregnancy, achieving a 91% detection rate at a 5% false positive rate for Down syndrome (and a 95% detection rate at a 0.3% false positive for trisomy 18 and 13). Part 1 of the Sequential Screen | Fß is essentially the same as the First Trimester Screen | Fß test.

Part 2 of the Sequential Screen | Fß

Part 2 of the Sequential Screen | Fß is performed in the second trimester of pregnancy, between 15 weeks and 21 weeks, 6 days gestation. This part of the test analyzes 4 biomarkers found in the mother's serum - alpha-fetoprotein (AFP), free beta hCG, unconjugated estriol, and inhibin-A. When the measurements from Part 2 are combined with those from Part 1, 94% of Down syndrome cases are detected at a 5.5% false positive rate and 95% of trisomy 18 and trisomy 13 cases are detected at a 0.3% false positive rate. Sequential Screen | Fß also screens for ONTDs, which can only be done in the second trimester. This test detects 90% of cases of open spina bifida and 98% of cases of anencephaly.

(References 13,26,31 Data on file, NTD Labs)