BCR-ABL (p210) Quantitation by PCR

Specimen Required

2 EDTA vials containing 3cc blood in each vial

Fasting Required

Purpose of the BCR-ABL (p210) Quantitation by PCR Test

To help diagnose and monitor the treatment of chronic myeloid leukaemia (CML) and a type of acute lymphoblastic leukaemia (ALL)

When this BCR-ABL (p210) Quantitation by PCR test is required

BCR-ABL testing is requested when a doctor suspects that a person has CML or Ph-positive ALL. Initial testing may be indicated when a person has non-specific symptoms such as fatigue, weight loss and/or an enlarged spleen or as a follow-up to abnormal findings on a FBC. Early in the disease, a person may have few or no symptoms. As time passes and normal blood cells are crowded out of the bone marrow and the number of abnormal leukaemic cells increases, a person may experience anaemia, prolonged bleeding, and recurrent infections.Once CML has been diagnosed, BCR-ABL quantitative genetic testing is requested periodically (typically every 3 months) to monitor the response to treatment and monitor for recurrence. If disease levels become very low and stable (a major molecular response) then the frequency of testing may change to 3-6 months though this will be determined by your doctor. If treatment resistance or disease recurrence occurs, the BCR-ABL kinase domain mutation analysis should be performed to guide further treatment.For patients with Ph chromosome-positive ALL, BCR-ABL quantitative testing will be requested periodically to coincide with treatment and as specified in any clinical trial that the patient may have enrolled in.

What the BCR-ABL (p210) Quantitation by PCR Test Detects

BCR-ABL refers to a gene sequence found in an abnormal chromosome 22 of some people with certain forms of leukaemia. Humans normally have 23 pairs of chromosomes, including 22 pairs of non-sex-determining chromosomes (also known as autosomes) and 1 pair of sex chromosomes (XX for females, XY for males). Chromosomes contain a person’s inherited genetic information. The genes that reside there form the blueprints for the production…BCR-ABL refers to a gene sequence found in an abnormal chromosome 22 of some people with certain forms of leukaemia. Humans normally have 23 pairs of chromosomes, including 22 pairs of non-sex-determining chromosomes (also known as autosomes) and 1 pair of sex chromosomes (XX for females, XY for males). Chromosomes contain a person’s inherited genetic information. The genes that reside there form the blueprints for the production of countless proteins. Sometimes changes can occur to a person’s chromosomes and/or genes during their lifetime, because of exposures to radiation, toxins, or for unknown reasons. The BCR-ABL gene sequence is one such acquired change that is formed when pieces of chromosome 9 and chromosome 22 break off and switch places. When this occurs, the ABL region in chromosome 9 fuses with the BCR gene region in chromosome 22. This is referred to as reciprocal translocation and this particular one is commonly expressed as t(9;22). A derivative chromosome 22 that has the BCR-ABL gene sequence is known as the Philadelphia (Ph) chromosome. It is strongly associated with chronic myeloid leukaemia (CML) and, less commonly with one type of acute lymphoblastic leukaemia (ALL) and rarely with acute myeloid leukaemia. At diagnosis, around 90-95% of cases of CML are found to have the Philadelphia chromosome. All cases have the BCR-ABL fusion gene, including the Philadelphia chromosome-negative cases. In this small fraction of cases the genes have fused on a more microscopic scale, not involving large chromosomal segments. These BCR-ABL gene sequences at the fusion site encode an abnormal protein. The abnormal BCR-ABL protein is a tyrosine kinase enzyme, a normal signalling protein which has become permanently switched “on” and is responsible for the development of CML and a type of ALL. When large numbers of abnormal leukaemic cells start to crowd out the normal blood cell precursors in the bone marrow, signs and symptoms of leukaemia start to emerge. Treatment of these leukaemias typically involves a tyrosine kinase inhibitor (TKI), given as daily tablets. Testing for BCR-ABL detects the Ph chromosome (the derivative chromosome 22) and BCR-ABL fusion gene or its transcripts, the RNA copies made by the cell from the abnormal stretches of DNA. The presence of the BCR-ABL abnormality confirms the clinical diagnosis in CML or a type of ALL. These are distinguished by the typical appearances of the cells through a microscope and, in the case of ALL, by flow cytometry (or “immunophenotyping”), which looks at molecules expressed inside the cells or more commonly expressed on the leukaemic cell surfaces. There are several different types of BCR-ABL test available, including:Cytogenetics (Chromosome analysis or Karyotyping) This test looks at chromosomes under a microscope to detect structural and/or numerical abnormalities. Cells in a sample of blood or bone marrow are grown in the laboratory and then examined to determine if the Philadelphia chromosome is present. Other chromosomal abnormalities can also be detected. Fluorescence in situ hybridization (FISH) This test method uses differently-coloured fluorescent dye-labelled probes to “light up” the BCR and the ABL gene sequences. Cells are examined under a microscope to determine the proportion if any where the coloured dots are fused together, indicating a BCR-ABL translocation. Genetic molecular testing, qualitative or quantitative The polymerase chain reaction (PCR)-based qualitative and quantitative tests detect and measure BCR-ABL gene transcripts, or gene product units, in a patient’s blood and/or bone marrow samples. This is the most sensitive test for BCR-ABL and is used to diagnose the minority of cases negative for the Philadelphia chromosome. It is also used to check the response to tyrosine kinase inhibitors (TKIs). Variant mutations of BCR-ABL can also be analysed if indicated. These mutations are responsible for treatment resistance to TKIs. If the response to treatment is suboptimal, mutational analysis may tell your doctor which TKIs will be more effective. How is the sample collected for testing? A blood sample is obtained by inserting a needle into a vein in the arm or a bone marrow sample is collected using a bone marrow aspiration and/or biopsy procedure. Is any test preparation needed to ensure the quality of the sample? No test preparation is needed. See MoreSee Less

Preparation for the BCR-ABL (p210) Quantitation by PCR Test

None

Sample Requirements

A blood sample taken from a vein in your arm or a bone marrow sample collected using a bone marrow aspiration and/or biopsy procedure

Additional Notes

Recognition of disease progression and transformation is important for prognosis and treatment. CML goes through three phases: Chronic phase—most patients with CML are diagnosed in chronic phase, which usually has an insidious onset. The chronic phase may last for several years. This is the phase when there are few or no symptoms and also the time period when treatment is most successful. Accelerated phase—changes include but are not limited to increasing white blood cell (WBC) counts, unstable platelet counts, blood basophils equal to or greater than 20%, additional cytogenetic changes, an increase in blasts in blood and/or bone marrow (but less than 20%) and lack of therapeutic response to standard treatment. Blast phase—when blasts equal or are greater than 20% of the blood white cells and/or of the nucleated (containing a nucleus) cells in the bone marrow, or when there is blast proliferation outside the bone marrow (apart from in the spleen).Both blood and bone marrow are often evaluated as part of the initial diagnosis, but the majority of follow-up monitoring is performed on blood samples. There is significant test variability among laboratories using different test platforms. Therefore, for a given patient, the quantitative BCR-ABL molecular testing should be done by the same laboratory or referred to a reference or accredited laboratory that follows universal reporting criteria. Rising and falling levels of BCR-ABL are usually more important than a single test result.

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