What is a BCR-ABL1 genetic test?
- Most people who have chronic myeloid leukemia (CML), which is also called chronic granulocytic leukemia or chronic myeloid leukemia
- Some people who have certain types of acute lymphoblastic leukemia (ALL)
- Some people with acute myeloid leukemia (AML), but very rarely
The abnormal BCR-ABL1 gene is made when two separate genes merge together and become one gene. Genes are short sections of DNA. DNA is made of long strands of material that carry information that controls what you look like and how your body works. DNA is packaged into structures in your cells called chromosomes. Normally, most of your cells have the same set of 23 pairs of chromosomes.
The abnormal BCR-ABL1 gene is formed when pieces of chromosomes 9 and 22 break off and trade places. The broken piece of chromosome 9 includes part of the ABL1 gene. It attaches (fuses) to part of the BCR gene on chromosome 22. This makes the abnormal fusion gene, BCR-ABL1. The changed chromosome 22 is called a "Philadelphia chromosome" after the city where researchers discovered it.
Your genes carry special instructions for making proteins that help your cells do their work. But the abnormal BCR-ABL1 gene has instructions for an abnormal protein. The protein causes certain bone marrow cells to make large numbers of abnormal white blood cells. These abnormal white blood cells are leukemia cells. They don't protect you from infections like healthy white blood cells do. They can build up in the blood and bone marrow and crowd out healthy blood cells.
There are different types of BCR-ABL1 genetic tests. They check your blood or bone marrow for:
- The abnormal BCR-ABL1 gene
- Changes in chromosome 22 that show it has become a Philadelphia chromosome
An abnormal BCR-ABL1 gene is an acquired genetic change. That means you don't inherit it from your parents, and you can't pass it on to your children. Acquired changes happen after birth if cells make a mistake when dividing to make new cells or if your DNA is damaged from exposure to substances that cause cancer. The changes show up only in certain types of cells. Changes in your genes are also called mutations or variants.
Other names: BCR-ABL, BCR-ABL fusion, Philadelphia chromosome, B-cell acute lymphoblastic leukemia (B-ALL), chronic myelogenous leukemia (CML), t(9;22), BCR-ABL1 Transcript Detection by RT-PCR, Quantitative BCR-ABL1 Translocation Detection by RT-PCR
What is it used for?
BCR-ABL1 genetic testing is most often used with other tests to diagnose or rule out two specific types of blood cancer:
- Chronic myeloid leukemia (CML).
- Philadelphia-positive acute lymphoblastic leukemia (Ph+ ALL). This is a type of acute lymphoblastic leukemia that has the Philadelphia chromosome.
Certain types of BCR-ABL1 testing may also be used to help plan treatment for these blood cancers. There are several treatment options. Some medicines target the protein made by the BCR-ABL1 gene. In general, these types of medicines cause less harm to normal cells than cancer chemotherapy or radiation therapy do.
During treatment, BCR-ABL1 tests may be used to see if cancer treatment working. And after treatment is finished, testing is often used to see if cancer is coming back.
Why do I need a BCR-ABL1 genetic test?
If your health care provider thinks you may have a type of leukemia that involves the BCR-ABL1 gene, you may need a BCR-ABL1 genetic test to make a diagnosis. Signs and symptoms of these blood cancers include:
- High levels of white blood cells on a complete blood count (CBC) test
- Weight loss
- Night sweats (heavy sweating during sleep)
- Joint or bone pain
- Pain or fullness below your ribs on the left side
- Painless lumps in your armpits, groin, neck, or belly
If you have already been diagnosed with a type of leukemia that involves a BCR-ABL1 gene, you may need this test to:
- Help guide treatment decisions
- See how well your treatment is working (if treatment is helping, the number of cells with BCR-ABL1 genes will decrease.)
- Monitor your health after treatment to see if blood cancer is coming back
What happens during a BCR-ABL1 genetic test?
A BCR-ABL1 genetic test usually uses a sample of blood or bone marrow.
If you are having a blood test, a health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
If you are having a bone marrow test, a provider usually takes a sample from the back of the hip bone. You will be given an injection (shot) of medicine to numb the area. You may also be given medicine to help you relax or sleep.
A bone marrow test has two parts that are usually done one after the other:
- For a bone marrow aspiration, the provider pushes a thin needle into the bone and removes a sample of bone marrow fluid with a syringe attached to the needle.
- For a bone marrow biopsy, the provider inserts a hollow needle into the bone and twists the needle to take out a small piece of bone marrow tissue. You may feel some pressure or brief pain while the sample is being taken.
The procedure takes only a few minutes. Afterwards, the area will be bandaged. You'll stay lying down for about 15 minutes to make sure the bleeding stops. You may need to stay longer if you had medicine to relax or sleep.
Will I need to do anything to prepare for the test?
You usually don't need any special preparations for a blood test. If you're having a bone marrow test, your provider will tell you whether you need to fast (not eat or drink) for a few hours before the procedure.
Are there any risks to the test?
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
After a bone marrow test, you may feel stiff or sore where the sample was taken. This usually goes away in a few days. If you need pain relief, talk with your provider.
What do the results mean?
If you had BCR-ABL1 genetic testing to diagnose a blood cancer, your provider will probably use the results of more than one test to make a diagnosis. Your provider will likely diagnose either chronic myeloid leukemia (CML) or Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) if your tests show all three of these results:
- Abnormal white blood cells
- The BCR-ABL1 gene
- The Philadelphia chromosome
In certain cases, a person may have CML without having the Philadelphia chromosome, but this isn't common.
If you had a BCR-ABL1 gene test to see if your cancer treatment is working, your provider will compare your results with past test results to look for changes over time. The way your results are reported depends on which test you had. Ask your provider to explain what your test results mean for your health and treatment plan. In general:
- If the amount of BCR-ABL1 in your sample decreases, it means your treatment is working to some degree. Your test results may describe your response to treatment using words such as minor, minimal, partial, major, or complete.
- If the amount of BCR-ABL1 in your sample increases, it may mean your treatment is not working. You may need to try another treatment or have more tests. An increase in BCR-ABL1 levels after successful treatment, may mean your cancer has come back.
Learn more about laboratory tests, reference ranges, and understanding results.
Is there anything else I need to know about a BCR-ABL1 genetic test?
Labs use different methods to test for the BCR-ABL1 gene and Philadelphia chromosome. The test method can affect your results. So, it's important to have your tests done the same way, and usually in the same lab. This allows your provider to compare your results over time. If you have questions about how your tests are done, ask your provider.
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