What Is The Integrated Screen?
The Integrated test is a two-stage screening that assesses the risk of a baby being born with Down syndrome, Trisomy 18, and Open Neural Tube Defects (ONTDs). The first stage can be performed between 11 weeks and 13 weeks and 6 days. The second stage can be performed between 15 and 22 weeks.
In the first stage, an ultrasound scan is used to precisely determine the gestational age of the pregnancy (to ensure that testing is being performed at the proper time.) An ultrasound measurement of the baby’s neck called a nuchal translucency is taken (NT and Nasal Bone Sonographer must be certified), and a blood sample is drawn to measure the level of pregnancy associated plasma protein (PAPP-A) and total b-hCG.
In the second stage, a second blood sample is taken to measure levels of four markers:
- Alpha-fetoprotein (AFP)
- Total beta-human chorionic gonadotropin (total ß-hCG)
- Unconjugated Estriol (uE3)
In pregnancies affected by Down syndrome, the levels of PAPP-A, AFP, and uE3 tend to be lower than normal while the levels of inhibin and total ß-hCG are elevated. The measurement from the NT may also be thicker than normal in an affected pregnancy.
In a pregnancy affected by ONTDs such as open spina bifida or anencephaly, the level of AFP tends to be elevated.
What Does A Screen Negative Test Result Mean?
- If the risk of Down syndrome is lower than 1 in 270, then the result is considered a screen negative result for Down syndrome.Although a screen negative test result means that the patient is not at high risk for having a baby with Down syndrome, a screen negative result does not completely rule out the possibility of a pregnancy with Down syndrome.
What Does A Screen Positive Result for Down Syndrome Mean?
- A screen positive result for the Integrated test means there is a risk of greater than or equal to 1 in 270 of a Down syndrome pregnancy. About 2.15% of patients who have the Integrated test receive a screen positive result.
Why Wait Until The Second Stage To Have A Risk Estimate?
- Using information from the first and second trimester yields a higher detection rate than a test using information from the first stage alone. Additionally, a test using only information from the first trimester cannot assess risk for ONTDs.