Chromosome Analysis and AFP, Amniotic Fluid
Also known as: Chromosome Karyotype and α-Fetoprotein (AFP), Amniotic Fluid
Use
Prenatal detection of chromosome abnormalities in at-risk pregnant women. AFP analysis of midtrimester amniotic fluid for detection of open neural tube and ventral wall defects. This test reflexes to AChE and fetal hemoglobin if AF-AFP is abnormal. While chromosome analysis is being performed, additional biochemical or molecular analysis can be performed.
Special Instructions
State gestational age (in weeks) on the day the sample was drawn on the test request form. The patient's gestational age must be between 12 weeks and 24 weeks for interpretation of AF-AFP. AChE false-positive and false-negative results are more frequent at gestational ages less than 13 weeks or greater than 24.9 weeks. Include a copy of the report if prior NIPT studies have been performed.
Limitations
No amniocytes in fluid, failure of cells to grow in culture, and/or contamination (e.g., by Mycoplasma) can preclude analysis. The overall culture success rate has been reported as 99% with a fetal loss (within four weeks of the amniocentesis) of 0.5%. This test was developed and its performance characteristics determined by Labcorp, and it has not been cleared or approved by the FDA.
Methodology
Chromosomal / Cytogenetics (FISH)
Biomarkers
LOINC Codes
- 1832-5
- 29253-2
- 49051-6
- 41273-4
- 72486-4
- 64095-3
- 64096-1
- 64092-0
- 64091-2
- 64093-8
- 62356-1
- 62357-9
- 48002-0
- 48672-0
- 11502-2
Result Turnaround Time
10-14 days
Related Documents
For more information, please review the documents below
Specimen
Amniotic Fluid
Volume
15-20 mL (20-30 mL for early amniocentesis)
Minimum Volume
10 mL
Container
Sterile plastic conical tube; do not use urine containers or tubes with rubber stoppers. Rubber is toxic to amniocytes.
Collection Instructions
Discard first 2 mL of fluid aspirated to avoid maternal cell contamination. Specimen is collected in a 20 mL sterile syringe and transferred aseptically to sterile tubes. Remove needle from syringe after collection. Samples from twin pregnancies should be labeled and placed in separate transport containers with a separate request form for each twin.
Storage Instructions
Maintain specimen at room temperature. Do not freeze or refrigerate.
Causes for Rejection
Suitability of specimen will be determined by the Cytogenetics laboratory upon receipt.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 1 month |