Fish T (15;17) LSI PML RARA Test

Fish –T-(15; 17)-LSI-PML-RARA Test

It is a cytogenetic test that is used in diagnosis of acute promyelocytic leukemia (APL). A cytogenetic test is a lab test which helps to study chromosomes and their structure. Humans have total of 46 chromosomes (23 pairs) in each cell with one pair inherited from mother and another from father .These chromosomes are made up of genes which are the basic unit of inheritance from parents to children. The total number of genes that a human has is called as genome. Genes are made up of DNA (deoxyribonucleic acid) molecules. These chromosomes carry all information for each cell to work efficiently.

The three main types of cytogenetic test are as follows:

• Karyotyping-it involves use of light microscopy and staining procedure to identify all chromosomes and look for abnormality such as aneuploidies(abnormal number of chromosomes) and translocations(part of chromosome breaks and attaches to another chromosome)
• Fluorescent in situ hybridisation (FISH)-it is an advanced and accurate test that maps the genetic material (DNA) present on the chromosomes in cells. It helps to look at specific gene or portion of gene to detect abnormality.
• Comparative genomic hybridisation (CGH) and array comparative genomic hybridisation (aCGH).

Leukemia is basically a cancer of blood in which a particular blood cell proliferates in uncontrolled and abnormal manner in the bone marrow and spreads to bloodstream and various organs of the body. The origin of this blood cancer is bone marrow of bones. One type of leukemia is acute promyelocytic leukemia (APL) in which there is translocation between chromosomes 15 and 17which causes fusion of promyelocytic leukemia gene (PML) present at chromosome 15 with retinoic acid receptor alpha gene (RARA) present at chromosome 17.this translocation can be detected by Karyotyping along with FISH assay. Hence this test is also called Fish karyotype test.

APL is treated with chemotherapy drugs like anthracyclines as well as non chemotherapy drugs like all-trans –retinoic acid (ATRA).sometimes stem cell transplant is also done.

Why is chromosomal karyotype test prescribed?

This Fish karyotype testis prescribed by health care provider for diagnosis of acute promyelocytic leukemia (APL) in a suspected individual. It is a type of acute myeloid leukemia which is very aggressive. It can present as following:

• Fever
• Easy fatigability/weakness
• Easy bruising/bleeding
• Recurrent infections
• Bone and joint pain
• Unexplained weight loss
• Loss of appetite

Procedure and prerequisites

The various types of samples which can be sent to laboratory for diagnosis of acute promyelocytic leukemia are as follows:

• Bone marrow aspirate
• Bone marrow biopsy
• Peripheral blood-it may be used if bone marrow is inaspirable
• Lymph node biopsy

Specimens should be collected before starting chemotherapy. Specimen should be collected from viable areas. Relevant clinical history/physical examination findings must be sent along with the sample. A properly filled requisition form must accompany the sample.