noninvasive prenatal screening and maternal serum screening · (part 1 and part 2) (mayo id:...
TRANSCRIPT
MATERNAL SERUM SCREENING Maternal serum screening is used in obstetric care to identify pregnancies that may have an increased risk for certain birth defects such as trisomy 21 (Down syndrome), trisomy 18, and open neural tube defects. These screening methods assess risk of fetal defects by measuring biochemical markers in maternal serum and in some cases also incorporate fetal nuchal translucency measurements obtained through sonography. Although a positive screen is not a diagnosis, pregnancies at higher risk are identified, and these patients can be offered diagnostic testing. Multiple screening options are available, including first trimester screening, second trimester screening, and cross-trimester screening. Cross-trimester screening has an improved detection rate and a decreased false positive rate as compared to either first or second trimester screening alone as this screening method incorporates markers from both trimesters in the risk calculation.
CELL-FREE DNA SCREENING More recently, an alternative screening method has emerged that measures risk by assessing fetal cell-free DNA in maternal serum. This screening method, which has been rapidly adopted, offers higher sensitivity and specificity for trisomy 21 and 18 than biochemical maternal screening methods and can be used as early as 10 weeks gestation. Cell-free DNA screening can also detect other aneuploidies including trisomy 13; it does not, however, detect open neural tube defects. This method of screening, frequently referred to as noninvasive prenatal screening, is also not diagnostic, and follow up with diagnostic testing for positive screens is recommended.
ACOG GUIDELINES The 2007 American Congress of Obstetricians and Gynecologists (ACOG) Screening for Fetal Chromosomal Abnormalities Practice Bulletin recommends that all women should be offered aneuploidy screening before 20 weeks of gestation, regardless of maternal age. Ideally, for women who present early in pregnancy, a strategy that incorporates both first and second trimester screening should be offered. The 2015 ACOG Committee Opinion for Cell-Free DNA Screening for Fetal Aneuploidy reiterates this recommendation of providing counseling to all women and discussing the risks and benefits of the available screening methods. This committee opinion states that any patient may choose cell-free DNA screening; however, conventional maternal screening methods are the most appropriate choice for low-risk pregnancies.
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Improving Patient Outcomes: Which test is best for your patient?
NONINVASIVE PRENATAL SCREENING AND MATERNAL SERUM SCREENING
MC6765-07rev0516
NONINVASIVE PRENATAL SCREENING
MATERNAL SERUM SCREENING
TEST NAME Cell-Free DNA Prenatal Screen(Mayo ID: NIPS)
First Trimester Maternal Screen(Mayo ID: 1STT)
QUAD Screen (Second Trimester) Maternal(Mayo ID: QUAD)
Sequential Maternal Screen (Part 1 and Part 2)(Mayo ID: SEQU/SEQF)
Alpha-Fetoprotein, Single Marker, Maternal Screen(Mayo ID: MAFP)
DESCRIPTION First or second trimester screen using cell-free DNA analysis.
First trimester screen using NT and biochemical markers.
Second trimester screen using biochemical markers.
Cross-trimester screen using NT and biochemical markers.
First trimester results provided only if positive, otherwise combined risk provided after second trimester screen.
Second trimester screen using single biochemical marker for NTD only.
SCREENS FOR Trisomy 21
Trisomy 18
Trisomy 13
Gender
Trisomy 21
Trisomy 18
Trisomy 21
Trisomy 18
Open NTD
Trisomy 21
Trisomy 18
Open NTD (If Part 2 is completed)
Open NTD
GESTATIONAL AGE (IN WEEKS)
10, 0 and up 10, 0 to 13, 3 (by CRL) T21/T18: 14, 0 to 22, 6
NTD: 15, 0 to 22,6
Part 1: 10, 0 to 13, 3 (by CRL)
Part 2: 15, 0 to 22, 6
15, 0 to 22, 6
MARKERS Cell-free DNA, chromosomes 21, 18, 13, and Y
PAPP-A
hCG (total)
NT
AFP
uE3
hCG (total)
inhibin
Part 1:
PAPP-A
NT
Part 2:
AFP
uE3
hCG (total)
inhibin
AFP
FALSE POSITIVE RATES FOR MAYO CLINIC VALIDATED TESTS
Trisomy 21: 0.09%
Trisomy 18: 0.13%
Trisomy 13: 0.13%
Trisomy 21: 5–10%
Trisomy 18: <1%
Trisomy 21: 6–7%
Trisomy 18: <1%
Open NTD: 2%
Trisomy 21: Part 1&2: 3–4%
Trisomy 18: Parts 1&2: <1%
Open NTD: Part 2: 2%
Open NTD: 2%
PROS Lowest false positive rate
Early results
Does not require NT measurement
Early results Includes trisomy and NTD screening
Does not require NT measurement
High-risk results available in first trimester
High detection rate with combined risk assessment
Single marker screen for NTD
Can complement first trimester screening or cfDNA screening
CONS Requires separate follow-up for NTD
Requires separate follow-up for NTD
Requires NT measurement by certified sonographer
Results not available until 2nd trimester
For most women, results not available until 2nd trimester
Requires NT measurement by certified sonographer
Requires coordination of two samples
Risk assessment limited to NTD
Abbreviations: AFP – alpha-fetoprotein; CRL – crown-rump-length; CVS – chorionic villus sampling; DS – Down syndrome; hCG – human chorionic gonadotropin; NT – nuchal translucency; NTD – neural tube defect; PAPP-A – pregnancy associated plasma protein A; uE3 – unconjugated estriol.