What are the other Names for this Test? (Equivalent Terms)
- BCR-ABL Fusion Test
- BCR-ABL Kinase Domain Mutation Analysis Test
- BCR-ABL Oncogene Test
What is BCR-ABL Test? (Background Information)
- BCR-ABL Testing helps in the diagnosis and monitoring of chronic myelogenous leukemia (CML) and ‘BCR-ABL-positive’ acute lymphoblastic leukemia (ALL)
- While, both these cancers affect the blood cells, CML begins from the blood-forming cells of myeloid line (that gives rise to cells, such as red blood cells, neutrophils, eosinophils, basophils, macrophages, and platelets), present in the bone marrow; while, ALL begins from the white blood cell precursors in the bone marrow
- The genetic information in the cell is contained in the DNA. DNA is organized into 23 pairs of chromosomes - 22 pairs of non-sex chromosomes, 1 pair of sex-determining chromosomes. Chromosomes contain genes - the genes are DNA sequences that contain information vital to life. They code for products that help cells live, grow, multiply, and also decide the characteristics of the cells, tissues, and the body, in whole
- Chronic myelogenous leukemia and certain types of acute lymphoblastic leukemia are caused by the product of abnormal BCR-ABL gene fusions.
- This is an abnormal gene sequence that is formed, when chromosome portions are mutually exchanged between chromosomes 9 and 22 - a piece of chromosome 9 breaks-off and joins with chromosome 22; while, similarly a piece breaks-off from chromosome 22 and fuses with chromosome 9
- This process, termed as ‘translocation’, produces an abnormal chromosome 22 with BCR-ABL gene sequence (often called Philadelphia chromosome) that guides the cells to multiply uncontrollably leading to cancer
- The BCR-ABL Tests are used to look for the BCR-ABL fusion gene and Philadelphia chromosome, or the product of the abnormal gene. These tests may be done on a sample of cells from bone marrow or blood. A group of such tests may include:
- Cytogenetics/Karyotyping: Chromosomes inside a cell are observed under a microscope for any abnormal shape or number
- Fluorescence in situ hybridization (FISH): Fluorescent probes, specific to BCR-ABL sequence are used to look for it. Such fluorescent probes attach only to specific DNA sequences
- Polymerase chain reaction (PCR): The PCR test helps to increase the number of copies of a particular gene sequence and then detects it
- Detecting the amount of BCR-ABL (quantitative testing)
What are the Clinical Indications for performing the BCR-ABL Test?
Following are the clinical indications for performing a BCR-ABL Test:
- Individuals with symptoms suggestive of either chronic myelogenous leukemia or acute lymphoblastic leukemia. Some of the common symptoms include:
- Loss of weight
- Loss of appetite
- Pain in the joints/bone
- Easy bruising/bleeding
- To investigate abnormalities found on a complete blood count
- To monitor patients with leukemia and to evaluate the treatment response, or to look for any recurrence of the condition
How is the Specimen Collected for BCR-ABL Test?
Following is the specimen collection process for BCR-ABL Test:
Sample required: Blood, bone marrow
- Blood: A blood sample is drawn through a needle inserted into the vein (arm)
- Bone marrow aspiration/biopsy:
- This procedure is done under mild sedation and/or local anesthesia
- Commonly, the sample of cells is obtained from the hip bone (other sites include the chest bone /sternum in adults and tibia/shin bone in infants)
- A special biopsy needle or a needle attached to a syringe is used to obtain a sample of cells from the bone marrow
- After sample collection, the puncture site is dressed. The site has to be kept dry for 48 hours
Preparation required: No special preparation is needed prior to the test.
What is the Significance of the BCR-ABL Test Result?
The significance of the BCR-ABL Test result is as follows:
- A presence of the Ph chromosome (Philadelphia chromosome) and BCR-ABL gene sequence indicates a diagnosis of either chronic myelogenous leukemia or Ph positive acute lymphoblastic leukemia
- Some CML patients may test positive for the BCR-ABL gene sequence, but not for the Ph chromosome
- A decreasing trend in BCR-ABL with treatment indicates a good response, and when levels are undetectable, it indicates a reduction/remission. Any increase in levels denotes disease progression or recurrence
The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.
Additional and Relevant Useful Information:
- The treatment for ‘BCR-ABL positive’ chronic myelogenous leukemia or acute lymphoblastic leukemia, is with a type of drug known as tyrosine kinase inhibitor (imatinib)
- Some cases of leukemia may show resistance to treatment with imatinib, which can be confirmed with additional testing for BCR-ABL Kinase Domain Mutations
Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.