BCR ABL1 Test; Purpose and test result

BCR-ABL1 genetic test

BCR ABL1 Test What is a BCR-ABL1 genetic test, when is it required of you, what are its types, and what are the implications of its results?

BCR ABL1 Test looks for a genetic mutation (change) on such a specific chromosome to evaluate patients with chronic myelogenous leukaemia.

BCR-ABL test overview

Chromosomes are the genetic components of your cells. Genes are pieces of DNA that have been passed down from your mother and father. They contain information that determines your individual characteristics, such as height and eye colour.

In each human cell, there are 46 chromosomes divided into 23 pairs. One pair of chromosomes is inherited from your mother, and the other pair is inherited from your father.
BCR-ABL1 is a mutation caused by the combination of two genes, BCR and ABL. It’s also known as a fusion gene, which encodes an abnormal protein involved in the development of  hematopoietic neoplasms, CML and a type of ALL.

A chimeric BCR-ABL1 mRNA transcript and corresponding translated oncoprotein are produced by the fusion gene on the derivative chromosome 22q11.

The altered chromosome 22, which contains the BCR-ABL transcript gene, is known as the Philadelphia kromosom after the city where it was discovered.

The BCR-ABL gene has a mutation that is not inherited from your parents. It is a somatic mutation, which means you did not inherit it. It comes later in life.

The BCR-ABL1 gene is found in people who have leukemia, a cancer of the bone marrow and white blood cells. BCR-ABL1 Fusion is found in nearly all patients with Chronic myelogenous leukaemia – CML.

The BCR-ABL gene has also been found in some patients with acute lymphoblastic leukaemia (ALL) and, in rare cases, acute myelogenous leukaemia (AML).

Brief Description for BCR-ABL1 test

Other names BCR/ABL, bcr-abl Oncogene, Philadelphia Chromosome,

  • BCR-ABL1 Fusion, CML monitoring, Tyrosine Kinase Inhibitor Resistance
purpose Identification of acquired BCR-ABL1 mutations associated with tyrosine kinase inhibitor (TKI) resistance in patients with chronic myelogenous leukaemia (CML) and a type of B-cell acute lymphoblastic leukaemia (ALL).
preparation There is no special preparation required
Specimen whole Blood or Bone Marrow Aspirate; collecting in Pink top tube (EDTA tube)
Criteria for Rejection
  • Serum or plasma.
  • Specimens collected in anticoagulants other than EDTA.
  • Frozen Specimens.
Turnaround Time 21 day
Reference range No variants detected (negative)
Methodology Whole blood is used to isolate RNA. For targeted next-generation sequencing (Illumina-based sequencing), Reverse Transcription-Polymerase Chain Reaction (RT-PCR) are used to detect variants in the ABL1 gene spanning amino acids

Types of BCR-ABL1 tests

There are several types of BCR-ABL1 tests available, including:

Cytogenetic (chromosomes analysis or karyotyping)

This test examines chromosomes under microscope to detect structural and/or numerical abnormalities.

The Philadelphia chromosome, for example, is a small abnormal version of kromosome 22 that results from the exchange or translocation of material between chromosomes 9 and 22. Cells from a blood or bone marrow sample (stem cells) are grown in the laboratories and examined to see if the Philadelphia chromosome is present.

Fluorescence in situ hybridization (FISH)

When the BCR-ABL1 gene sequence is present, fluorescent dye-labeled probes “light up.” FISH test results are frequently available faster than conventional chromosome analysis.

Molecular genetic testing (qualitative or quantitative)

Qualitative and quantitative polymerase chain reaction (PCR) tests detect and quantify BCR-ABL1 RNA transcripts in leukaemia cells isolated from blood or bone marrow samples.

This test can detect very small amounts of BCR-ABL even when the Philadelphia gene is not visible in bone marrow cells using less sensitive but still important techniques such as chromosome analysis or FISH.

DNA sequencing methods

Secondary mutations in BCR-ABL1 are known to cause therapy resistance. DNA sequencing methods can used for detection.

purpose of BCR-ABL1 genetic test

A BCR-ABL1 may be required. When you have a CBC result and/or symptoms of chronic myeloid leukaemia (CML) or acute lymphoblastic leukaemia (ALL). These include:

  • Fatigue
  • fever
  • weight loss
  • Sweating at night (excessive sweating while sleeping)
  • Joint or bone discomfort
When CML and ALL are detected early, they are easier to treat.

Depending on where the chromosome 22 break occurred, BCR-ABL1 can produce proteins of varying sizes and weights. In CML, the BCR breakpoint is almost always in the major breakpoint cluster region (M-BCR), resulting in the production of a larger BCR-ABL1 protein (the protein is called p210). Breaks in the minor breakpoint cluster region (m-BCR) result in a shorter fusion protein (known as p190), which is most commonly associated with Ph chromosome-positive ALL.

The quantitative BCR-ABL1 molecular test assesses either of the fusion gene’s breakpoints. It is used to establish a baseline value and then to monitor the person’s response to treatment, as well as to monitor for recurrence if the person achieves complete recovery.

What happens during a BCR-ABL1 test?

A BCR-ABL  is typically a blood test or a bone marrow aspiration and biopsy.

Blood sample

A blood test involves a health care professional drawing blood from a vein in your arm with a small needle. Following the insertion of the needle, a small amount of blood will be collected in a tube (EDTA tube) or vial. This usually takes near five minutes.

Bone marrow aspiration

Bone marrow aspiration

If you are having a bone marrow aspiration and biopsy, the following steps may be taken:

  • Depending on which bone will be tested, you will lie on your side or stomach.
The hip bone is used for the majority of bone marrow tests.
  • Your body will be clothed so that only the area around the testing site is visible.
  • An antiseptic will be used to clean the site.
  • You will be injected with a numbing solution.
  • The health care provider will take the sample after the area has been numbed.
  • During the tests, you must remain completely still.
  • A bone marrow aspiration, involves inserting a needle through the bone and extracting bone marrow fluid and cells.
  • When the needle is inserted, you may experience a sharp but brief pain.
  • A bone marrow biopsy involves the use of a special tool that twists into the bone to extract a sample of bone marrow tissue.
  • While the sample is being taken, you may feel some pressure on the site.
  • The health care provider will apply a bandage to the site.

Is the test risky?

A blood test carries very little risk. You may experience minor pain or bruising where the needle was inserted, but most symptoms subside quickly.

You may experience stiffness or soreness at the injection site after a bone marrow test. This usually resolves itself within a few days. To alleviate pain, your doctor may recommend or prescribe a pain reliever.

“Related: C peptide test; Precautions and Results Interpretation

BCR-ABL1 test resuls

The presence of BCR-ABL gene as well as an abnormal number of white blood cells, likely might be diagnosed with chronic myeloid leukaemia (CML) or (Ph)-positive, acute lymphoblastic leukaemia (ALL).

If you are receiving treatment for CML or Ph- positive (ALL), your results may reveal:

  • BCR-ABL levels rised:  This could mean that your treatment isn’t working or that you’ve developed resistance to the tyrosine kinase inhibitor (TKI) used to treat them.
  • BCR-ABL levels decreased: This could imply that your treatment is effective, and the patient is responding to treatment.
  • BCR-ABL levels not changed: This could indicate that your disease is under control.

Why would BCR-ABL1 analysis performed multiple times?

Your doctor may order BCR gene analysis on a regular basis to see if you have developed any new chromosome abnormalities. Additional changes are frequently observed as the disease progresses and accelerates.

Patients with chronic myeloid leukaemia (CML) and Ph-positive acute lymphoblastic leukaemia (ALL) have responded well to treatment. It is critical to see your doctor on a regular basis to ensure that your treatments are still effective. If you develop resistance to treatment (BCR-ABL levels increased), your doctor may suggest a different type of cancer treatment.

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