CellFree DNA Prenatal Screen
General Information
Lab Name
CellFree DNA Prenatal Screen
Lab Code
PDNAS
Epic Name
Cell-Free DNA Prenatal Screen
Description
- The Cell-Free DNA Prenatal Screen assesses the copy number state for ALL 46 chromosomes, which allows for evaluation of both common aneuploidies (trisomy 13, 18, 21) and rare autosomal aneuploidies.
- This screen does not provide diagnostic information. False-positive and/or false-negative results are possible. Thus, individualized patient-provider discussion is highly recommended prior to ordering, and clinical correlation is recommended for all results. Diagnostic testing should be offered to confirm screening results prior to any medical management decisions.
- This screen is validated for individuals with a singleton or twin pregnancy of at least 10 weeks gestation and does not assess for neural tube defects.
- Medical factors of the pregnant individual and/or chromosomal mosaicism in the placenta, the fetus(es), or the pregnant individual may impact results.
- There are several differences in the information available from this screening test in singletons compared to twins:
- Aneuploidy of the X or Y chromosome is evaluated only in a singleton pregnancy. It is not evaluated in twins.
- Evaluation of both sex chromosomes is available upon request in singleton pregnancies. In twin pregnancies, evaluation for the presence of a Y chromosome is available upon request. If Y chromosome material is detected in a twin gestation, this screen cannot distinguish whether it is present in one or both fetuses.
- Positive screening results in twin gestations cannot resolve whether one or both fetuses are at risk.
Ordering Requirements
Singleton and twin pregnancies
For orders submitted electronically via Epic, providers must complete the clinical questions in the order.
Submissions from outside (reference lab) clients must be accompanied by a completed UW Genetics Clinical Lab Request form.
This screen is not validated for triplets or higher order multiple gestations.
Synonyms
cell-free fetal DNA, cfDNA, Down syndrome, fetal chromosome aneuploidy screen, NIPS, NIPT, noninvasive prenatal screening, noninvasive prenatal testing, Placental DNA, Trisomy 13, Trisomy 18, Trisomy 21, Turner syndrome, twin
Components
Code | Name |
---|---|
PDNAP | cfDNA Panel |
PDNAX | cfDNA Sex Chromosomes |
PDNAR | cfDNA Result |
PDNAI | cfDNA Interpretation |
PDNAF | cfDNA Predicted Fetal Fraction |
PDNAC | cfDNA Comment |
PDNAM | cfDNA Method |
PDNAGC | cfDNA Genetic Counselor |
PDNADI | cfDNA Director |
Interpretation
Method
Massively parallel sequencing of total cell-free DNA (cfDNA)
Reference Range
See individual components
Guidelines
Ordering & Collection
Specimen Type
Collection
Two 10 mL whole blood in Streck Cell-Free DNA BCT® tubes (mottled black and tan).
Gently mix blood by inverting tube 8-10 times.
Do not send samples via pneumatic tube system. Samples collected in Streck tubes must be walked to the laboratory.
Forms & Requisitions
UW Genetics Clinical Lab Request
Handling Instructions
Walk samples to the laboratory after collection. Do NOT use the pneumatic tube system, as this may compromise the sample.
Quantity
requested: 20 mL whole blood
minimum: 7 mL whole blood
Processing
Store whole blood at room temperature. Do not freeze. For orders not placed in Epic, a completed UW Genetics Clinical Lab Request form is required.
At the cfDNA Panel (PDNAP) prompt:
- Singleton:
- Enter PSFULL for Full prenatal screen for all 46 chromosomes, autosomes PLUS sex chromosome aneuploidies.
- Enter PSAU for Limited prenatal sreen for autosomes ONLY.
- Twin:
- Enter PTFULL for Full prenatal screen for all 46 chromosomes, autosomes PLUS presence of Y chromosome.
- Enter PTAU for Limited prenatal screen for autosomes WITHOUT the Y chromosome.
Stability: Ambient, 5 days.
Performance
LIS Dept Code
Genetics (GEN)
Performing Location(s)
UW-MT |
Genetics
Attention: Genetics Lab Tel: 206-598–6429 M–F (7:30 AM–4:00 PM) Tel (EXOME only): 206-543-0459 |
Faculty |
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Frequency
Turnaround time 8-10 business days
Available STAT?
No