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Products of Conception Aneuploidy Evaluation by Fluorescence In Situ Hybridization (FISH) Analysis

FISH, POC FISH, genetic, GPOC2, POC Aneuploidy Detection Panel (13, 16, 18, 21, 22, X, Y)

Test Codes

EPIC: LAB6700

Department

Cytogenetics

Specimen Collection Criteria

Collect: Paraffin-embedded tissue section. This test is only performed on tissue sections known to contain fetal tissue or chorionic villi. A pathologist will designate the region of interest on an H & E slide.

A copy of the requisition must be sent with the specimen. 

Rejection Criteria

Specimens that do not contain adequate fetal tissue or chorionic villi as determined by a pathologist cannot be performed.

In-Lab Processing

Specimens are processed immediately upon receipt in the Laboratory. Store tissue in tissue culture medium.

Storage

Specimen Stability for Testing:

Specimens are stable at room temperature (20-26°C or 68-78.8°F) for 24 hours prior to testing.

Specimen Storage in Department Prior to Disposal:

Processed FISH slides are stored in the freezer (-20°C) for one year after the case has been signed out.

Laboratory

Royal Oak Cytogenetics Laboratory

Performed

Monday – Friday, 8:00 am – 5:00 pm.
Results available within 7 days of receipt in the Laboratory.

Reference Range

Positive or negative for chromosome aneuploidy. An interpretative report will be provided.

Test Methodology

Fluorescence In Situ Hybridization (FISH) Analysis.

Interpretation

Aneuploidy is detected when the percentage of nuclei with an abnormality exceeds the threshold (normal reference range) established for each probe. An aneuploid conception is associated with an increased risk of up to 1% beyond the age-related risk for aneuploidy in future pregnancies.

Clinical Utility

Products of conception (POC) refer to tissues present in a fertilized gestation that are collected at the time of pregnancy termination or miscarriage. These tissues include chorionic villi, fetal membranes, and fetal tissue. While many causes of spontaneous miscarriage have been identified, a chromosome abnormality is observed in up to half of all cases. Thus, cytogenetic examination of POC tissues is important to ascertain a potential cause of the pregnancy loss. Chromosome aneuploidy, the gain or loss of chromosomes, is a major cause of early fetal demise. The gain of a chromosome (trisomy) accounts for a large percentage of aneuploidy identified in miscarried fetuses, most commonly involving chromosomes 13, 16, 18, 21, and 22. Other common numerical chromosome abnormalities identified in miscarriages include loss of the X chromosome (Turner syndrome) and triploidy (69 chromosomes instead of the normal diploid content of 46 chromosomes). 

Conventional cytogenetic analysis of POC tissue will often identify aneuploidy as the cause of pregnancy loss; however, 20% of such specimens fail to grow in culture. Without further evaluation, a common potential cause of the fetal demise will fail to be identified. A FISH panel has been developed to evaluate this subset of patients. Utilizing paraffin-embedded tissue sections made at the time of pathological evaluation of the POC tissue, DNA probes to enumerate chromosomes 13, 16, 18, 21, 22, X, and Y are utilized. This test is only performed on tissue sections known to contain fetal tissue or chorionic villi.

Reference

1. Lescoat D et al (2005): Fluorescent in situ hybridization (FISH) on paraffin-embedded placental tissues as an adjunct for understanding the etiology of early spontaneous abortions. Prenat Diagn 25:314-317.

CPT Codes

88271x7 (DNA probe, each), 88275x3 (Interphase analysis, 100-300 cells).

Contacts

Last Updated

12/30/2022