FISH (Fluorescence in situ hybridisation)

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

Specimens must be delivered fresh to the laboratory.

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.