Chromosome FISH, Amniotic Fluid with Reflex to Chromosome Analysis or Genomic Microarray

Casandra

Casandra Test Code AR85227Version 1 (DRAFT)

Performing Lab

Lab ARUP LaboratoriesLab Test ID 2011130CPT Codes 81229, 81265, 88235, 88269, 88271, 88275

Chromosome FISH, Amniotic Fluid with Reflex to Chromosome Analysis or Genomic Microarray

Also known as: AF F RFLX

Clinical Use

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Use

This test is used for the rapid detection of aneuploidy involving chromosomes 13, 18, 21, X, and Y from amniotic fluid. If the FISH results are abnormal, the specimen reflexes to chromosome analysis to determine the mechanism of the abnormality. In cases where the FISH results are normal, the specimen is reflexed to a genomic microarray. This testing process helps in quickly identifying and analyzing chromosomal abnormalities in a prenatal context, which can be critical for clinical decision-making related to chromosomal abnormalities.

Special Instructions

Prenatal Cytogenetics Patient History Form and informed consent for genetic testing are required. The test must be ordered using the Cytogenetic test request form #43098 or through the ARUP interface. Specimen and the completed test request form, including clinical indication, must be received within 48 hours of collection. For correct processing, avoid freezing or exposing the sample to extreme temperatures. Counseling and informed consent are recommended; consent forms are available online.

Limitations

The FISH analysis does not detect structural chromosome abnormalities, mosaicism, and other numerical chromosome abnormalities excluding chromosomes 13, 18, 21, X, and Y. Additionally, false-positive or false-negative results, as well as maternal cell contamination, have been demonstrated in prenatal FISH analysis. Chromosome analysis studies involve the culturing of living cells, and turnaround times may vary due to multiple variables. The American College of Medical Genetics recommends that irreversible therapeutic action should not be initiated based solely on FISH results. The genomic microarray analysis cannot provide structural information associated with genomic imbalances and cannot detect certain genomic alterations, such as CNVs below the limit of resolution of the platform, sequence-level variants including point mutations, indels, low-level mosaicism, balanced chromosomal rearrangements, and genomic imbalances in repetitive DNA regions.

Test Details

Methodology

Chromosomal / Cytogenetics (FISH)

Biomarkers

This component involves the use of Fluorescence in situ Hybridization (FISH) for identifying aneuploidy of chromosomes 13, 18, 21, X, and Y in amniotic fluid.

Chromosome FISH, Prenatal • FISH