cell-free maternal DNA testing (Prenatal cell-free DNA screening, Noninvasive prenatal testing [NIPT], cell-free DNA in maternal blood, cf DNA screening)
المؤلف:
Kathleen Deska Pagana, Timothy J. Pagana, Theresa Noel Pagana.
المصدر:
Mosbys diagnostic and laboratory test reference
الجزء والصفحة:
15th edition , p219-220
2025-11-04
52
Type of test Blood
Normal findings
Low risk of chromosomal abnormality
Test explanation and related physiology
Trisomy 21 (Down syndrome), trisomy 18 (Edwards syn drome), and trisomy 13 (Patau syndrome) are the three most common chromosomal abnormalities affecting live births. Although 1 in 450 live births has one of these aneuploidy abnormalities, trisomy 21 is the most common. Abnormal findings on pelvic ultrasonography of the fetus, including fetal nuchal translucency or thickness along with biochemical markers (e.g., hCG; PAAP-A,), can identify pregnancies at high risk for these chromosomal defects. The definitive diagnosis requires chorionic villus sampling (CVS) and amniocentesis, which are invasive and increase the risk for miscarriage.
Cell-free (cf) DNA from the placental fetal cells circulates in maternal blood. This DNA can be extracted and, through advanced laboratory techniques of targeting genomic sequencing, allows 99% of the cases of trisomy to be detected. False positive rates instigating unnecessary invasive testing are less than 1%. This testing can be performed as early as 10 weeks of gestation but is typically done between 10 and 22 weeks. Because of newer laboratory techniques of multiplexing, results can be available in about 1 week.
In 2012, the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM) issued a joint committee opinion that supported noninvasive prenatal testing that uses cell-free fetal DNA for women at increased risk for having a baby with a chromosomal abnormality (Box 1).
Box1. Women at high risk for having children with chromosomal abnormalities
Testing of high-risk pregnant women may be done in several ways:
• cf DNA test done in the first trimester along with ultrasonography
• cf DNA test done in the second trimester without ultrasonography C
• A combination of both
Procedure and patient care
• See inside front cover for Routine Blood Testing.
• Fasting: no
• Blood tube commonly used: red
* Encourage all women undergoing cf DNA to have genetic counseling.
* Results should be reviewed with the patient, and the risks, benefits, and alternatives to further testing should be explained.
Abnormal findings
- Trisomy 21 (Down syndrome)
- Trisomy 18 (Edwards syndrome)
-Trisomy 13 (Patau syndrome)
- Duchenne muscular dystrophy
- Hemophilia
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