FISH (Fluorescence in situ hybridisation)

Last updated: Monday, 06, August, 2007

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Item Process
Specimen

Blood, bone marrow (collected in sterile, preservative-free heparin), tumour, placenta, foetal tissue or amniotic fluid.

Specimens must be delivered fresh to the laboratory.

Method

Slides are prepared directly from the specimen or after cell culture.

Metaphase or interphase preparations are used.

Specific fluorescent DNA probes are hybridised to chromosomal DNA. Multiple loci can be probed simultaneously.

Application

FISH is a sensitive and useful adjunct to cytogenetic testing for the detection of abnormalities of chromosomal structure or numbers (eg, deletions, translocations, duplications, aneuploidy). It is often the method of choice for detection of microdeletions.

Prenatal: Interphase FISH is a rapid diagnostic test when one of the commonly occurring trisomies (21, 18, 13) or a sex chromosome abnormality is suspected. It is a useful adjunct but cannot replace full karyotyping.

Oncology: FISH can detect a number of translocations (eg, BCR-ABL; MLL; PML/RARA; TEL/AML1) associated with haematological malignancies and can be used to monitor minimal residual disease after chemotherapy and/or bone marrow transplantation.
It can also detect gene amplifications (eg, MYC/MYCN) associated with an adverse prognosis for certain tumours.
Following sex mismatched bone marrow transplantation, FISH can be used to confirm engraftment.

In disorders such as CLL or multiple myeloma where it may be difficult to induce malignant cells to divide, interphase FISH can detect abnormalities of prognostic significance.

Interpretation

FISH provides a sensitive method to identify chromosomal abnormalities and rapid assessment of large numbers of cells (>500). It is highly accurate, for the probe, in identifying the origin of the chromosome or chromosomal fragment under investigation.

Consult pathologist.

Reference

Smith A. RPCA Broadsheet 1995; No. 37. 

Le Beau M. Nature Genetics 1996; 12: 341-344.

Caine A. et al. Lancet 2005; 366: 123-128.