Products of Conception (POC) Aneuploid Evaluation, FISH Genetics

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Test Details

Synonyms

  • Aneuploid Fluorescence in situ Hybridization
  • POC FISH

Use

Rapid identification of common aneuploidies (specific for X, Y, 13, 16, 18, 21, 22) as the cause of miscarriage.

Limitations

Molecular mutations below the resolution of FISH will not be detected. Will not detect regions not targeted by FISH probes in this panel.

This test was developed, and its performance characteristics determined, by LabCorp. It has not been cleared or approved by the US Food and Drug Administration (FDA).

Methodology

Fluorescence in situ hybridization (FISH)

Specimen Requirements

Specimen

Chorionic villi, amniotic fluid, fixed-cell pellet from a cytogenetic analysis, slides from a fixed-cell pellet with metaphase and/or interphase nuclei

Volume

• Chorionic villi: 30 mg

• Amniotic fluid: 5 mL

• Fetal tissue: 4x4x4 mm

• Fixed-cell pellet from a cytogenetic analysis

• Eight slides from a fixed-cell pellet with metaphase and/or interphase nuclei

Minimum Volume

• Chorionic villi: 5 mg

• Amniotic fluid: 3 mL

• Fetal tissue: 2x2x2 mm

• Fixed-cell pellet from a cytogenetic analysis

• Four slides from a fixed-cell pellet with metaphase and/or interphase nuclei.

Note: Minimum volumes may not allow for repeat testing.

Container

CVS samples: CVS transport tube available from the cytogenetics laboratory (email: CMBP_CytoPrenatal); sterile container with transport mediaAmnio samples: Sterile plastic conical tubeFetal tissue samples: Sterile container with sterile Ringer's lactate or Hank's balanced salt solution or transport medium provided by cytogenetics laboratory. Do not use urine containers for shipping.

Collection

CVS samples: Specimen is collected in syringe (transabdominal) or catheter (transcervical) and transferred by flushing with the media from the sterile container back into it. After collecting the specimen, wash with sterile saline solution (NaCl 0.95%) containing sodium heparin (two to three drops of sodium heparin in 10 mL of saline). Carefully transfer the specimen, into the CVS transport tube, using a sterile Pasteur pipette or a sterile fine needle forceps. Be sure to fill transport tubes completely with media.

Amnio samples: 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 to be transported to LabCorp. Request form is completed and accompanies specimen and miscellaneous slip to the laboratory.

Fetal tissue samples: Aseptically obtain a small piece of tissue with subepidermal layers. Best results are obtained from placental villi, which remain viable much longer than fetal tissue. This is especially true in stillborn cases in which both cord blood and tissue samples are often not viable. If specimen is a product of conception, submit biopsies in a sterile tube with sterile Ringer's lactate, Hanks' basal salt solution, or LabCorp transport medium.

All sample types: Transport to the testing laboratory at room temperature is acceptable. Do not allow the sample to over heat or freeze. Use a cool pack or LabCorp transport kit if necessary.

Storage Instructions

Maintain specimen at room temperature and transport to the cytogenetics laboratory immediately. Do not freeze. Refrigerate if sterility is questioned or if sample cannot be shipped within 24 hours.

Causes for Rejection

Contaminated specimen; amino specimen received in a container with a rubber stopper (rubber is toxic to amniocytes); maternal decidua received; frozen specimen; absence of villi or fetal tissue; broken or stained slides; low volume or quantity not sufficient for analysis

Clinical Information

Special Instructions

Refer to Paraffin FISH, POC Aneuploid [511880] for formalin-fixed or paraffin-embedded tissue. Pertinent medical findings and gestational age should accompany request for FISH. It is recommended that this test be run concurrently with Chromosome Analysis, Tissue Biopsies (Products of Conception, Skin) [052052]. Note: This test number is used for tracking FISH specimens to the testing laboratory. Bill codes will be added when testing is complete based on the processes performed in the laboratory.

References

Gouny C, Bonnet-Dupeyron MN, Cherasse Y, et al. Chorionic villus samples (CVS) and fluorescence in situ hybridization (FISH) for a rapid first-trimester prenatal diagnosis. Prenat Diagn. 2004 Apr; 24(4):249-256. 15065097
Tepperberg T, et al. Prenatal diagnosis using interphase fluorescence in situ hybridization (FISH): Two-year multi-center retrospective study and review of the literature. Prenat Diagn. 2001; 21:293-301.8488836

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