FISH ANALYSIS, PRENATAL ANEUPLOIDY SCREEN
TURNAROUND TIME: 1 to 2 days
TESTING METHODOLOGY: Fluorescence in situ hybridization
- Collect: 20 - 30 mL amniotic fluid in sterile centifuge tubes or bottles; discard the first 2 mL collected to reduce risk of maternal cell contamination
- Min. Collection: 20 mL amniotic fluid; smaller volumes will be assessed to determine whether adequate for FISH testing
- Transport: 20 - 30 mL amniotic fluid in sterile centrifuge tubes at 20-25°C
- Stability: Ambient: 24 hours; Refrigerated: 24 hours Frozen: unacceptable
- Unacceptable Conditions: Frozen or non-sterile specimens; grossly bloody specimens unacceptable for FISH
A Prenatal Diagnosis Information Form and a Cytogenetic Laboratory Test Requisition Form must accompany the specimen. Contact the Cytogenetics Laboratory at 918-502-1722 to obtain further information.
Test Summary: Rapid detection of the most common numerical chromosome abnormalities - aneuploidy of chromosomes X, Y, 13, 18 and 21
Methods: Dual-color and triple-color FISH analyses performed on interphase nuclei using probes for the X and Y chromosomes (DXZ1 and DYZ3) and chromosome 18 (D18Z1) and probes for the RB1 locus on chromosome 13 and the D21S259, D21S341, and D21S342 loci on chromosome 21; analysis of 50 interphase cells for each probe set.
Test Limitations: Complete or partial trisomies and structural rearrangements of chromosomes other than chromosomes 13, 18, 21, X and Y are not detected; structural rearrangements of chromosomes 13, 18, 21, X and Y may not be detected. Low levels of mosaicism involving chromosomes 13, 18, 21, X and Y may not be detected. There may be problems in interpretation of results in cases of maternal cell contamination.
FDA Approval: This test is FDA approved for in vitro diagnostic testing.
Test Variables: Turnaround time given represents average time which is subject to multiple variables. Specimens received on Friday will not be reported until following Tuesday.
Indications for Use:
- Pregnancies at risk for trisomy 13, trisomy 18, trisomy 21, or numerical abnormalities of the sex chromosomes due to abnormal ultrasound findings, abnormal maternal serum screening results, or advanced maternal age