Chromosome Analysis, Product of Conception Reflex Testing to Fish for Aneuploidy Detection

Description

This test aids in identifying the chromosomal reasons of foetal death and estimating the likelihood that similar pregnancy losses may occur again. Chromosomal anomalies can cause spontaneous abortions, deformed foetuses, or neonatal mortality. With chromosomal anomalies, spontaneous abortions occur between 15 and 60% of the time.

Methodology

Harvest/Hybridization/Microscopy/Interpretation

Prerequisites for Specimens

Analysis is possible on the placenta, umbilical cord, and internal foetal organs. Please send chorionic villi if at all possible.

Transport media or sterile saline in sterile, leak-proof containers (i.e. Hanks Balanced Salt Solution). Don't submerge in formalin.

Maximum Amount: 1x1x1 cm of at least two foetal tissues, one of them being chorionic villi.

1 foetal tissue is the minimum quantity.

Maintaining at Room Temperature

8 hours of stability at room temperature, then refrigerate

Avoid freezing or overheating when travelling.

Time to Complete

90% of cases receive their final report in 24–48 hours.

Clinical Importance

A sensitive way to find chromosome abnormalities is fluorescence in situ hybridization (FISH). FISH is a quick and accurate technique for detecting chromosome abnormalities in a prenatal context because of its capacity to detect the most frequent aneuploidy in uncultured amniocytes quickly (within 24-48 hours). However, routine chromosomal analysis cannot be replaced by FISH technology, which is why FISH diagnostic testing is not advised as a stand-alone test without chromosome analysis for the diagnosis of the most frequent aneuploidy diseases.

Clinical context

The tissue viability is one of the main restrictions with regard to chromosomal analysis on products of conception. Failure to obtain chromosome data can have serious clinical repercussions for the parents because more than 50% of first trimester abortuses have chromosome abnormalities. Up to 25% of samples may not receive any chromosomal results as a result of reduced viability.

Rapid FISH analysis can, however, get over this tissue viability restriction because it can be used on non-viable tissues during the interphase. Although trisomy of chromosome 16 and monosomy X account for the majority of chromosome abnormalities in first trimester abortuses, fast interphase FISH utilising probes for the most prevalent aneuploidies can still yield results in situations when conventional chromosome analysis fails. If standard chromosomal analysis is unsuccessful, FISH on uncultured products of conception samples may be a useful and practical option. In our lab, we provide a reflex test to perform interphase FISH on samples of uncultured products of conception that did not succeed in culture.

Methods

Samples of uncultured products of conception are taken, cleansed for maternal decidua, and hybridised with the chromosome 13, 16, 18, 21, X, and Y probes. The slides are examined using a fluorescence microscope outfitted with an epifluorescence and the necessary filter sets after hybridization and post-hybridization washes. Two certified technologists conduct the analysis and scoring in a blinded manner, with each scoring a minimum of 50 interphase nuclei. The director and the lab manager both review the results.