A beta-2 microglobulin tumor marker test measures the amount of a protein called beta-2 microglobulin (B2M) in your body fluids. The test usually uses a sample of your blood. It may also be done using urine (pee) or in rare cases cerebrospinal fluid (CSF).
B2M is a type of tumor marker. Tumor markers are substances that are often made by cancer cells or by normal cells in response to cancer in the body. B2M is found on most of the cells in your body. Normally, you have only small amounts of B2M in your blood and urine. High levels of B2M in body fluids are often caused by these blood and bone marrow cancers:
- Multiple myeloma
- Chronic lymphocytic leukemia (CLL)
- Certain types of lymphoma
A beta-2 microglobulin tumor marker test can’t diagnose cancer or any other condition. That’s because there are so many conditions that can cause high levels of B2M. But if you’ve already been diagnosed with one of these blood and bone marrow cancers, a B2M test can provide important information about your cancer including:
- How much cancer you have in your body and how fast it’s growing
- How your cancer may behave in the future
- How much your treatment is helping
This information can help you and your health care provider plan your care.
Other names: total beta-2 microglobulin, β2-microglobulin, B2M, B2MG, thymotaxin
What is it used for?
A beta-2 microglobulin tumor marker test is most often used if you have been diagnosed with certain cancers of the bone marrow or blood. Testing your B2M levels can help:
- Find out how much cancer is in your body
- Predict how your cancer will develop
- Pick your treatment and check whether it’s working
- Check whether cancer has spread to your brain and/or spinal cord (This is done only if you have symptoms.)
Why do I need a beta-2 microglobulin tumor marker test?
If you have been diagnosed with multiple myeloma, chronic lymphocytic leukemia, or certain types of lymphoma, you may need a B2M test to find out how serious your disease is. B2M testing can help monitor your cancer and check whether your treatment is working.
If you have multiple myeloma, you may need a B2M test to see whether your cancer is spreading. A test of a urine sample may also be needed to check whether your disease is affecting your kidneys.
What happens during a beta-2 microglobulin tumor marker test?
A beta-2 microglobulin test usually uses a sample of your blood. In certain cases, you may need to provide a 24-hour urine sample, which means collecting all your urine for a full day. If your provider suspects that cancer has spread to your brain or spine, you may have a cerebrospinal fluid (CSF) analysis.
For 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.
For a 24-hour urine sample, you will be given a special container to collect your urine and instructions on how to collect and store your samples. Your provider will tell you what time to start. The test generally includes the following steps:
- To begin, urinate (pee) in the toilet as usual. Do not collect this urine. Write down the time you urinated.
- For the next 24 hours, collect all your urine in the container.
- During the collection period, store the urine container in the refrigerator or in a cooler with ice.
- 24 hours after starting the test, try to urinate if you can. This is the last urine collection for the test.
- Return the container with your urine to your provider’s office or the laboratory as instructed.
For a cerebrospinal fluid (CSF) analysis, a provider will do a procedure called a spinal tap (also known as a lumbar puncture). A spinal tap is usually done in a hospital. A provider numbs your skin with medicine and uses a thin, hollow needle to remove some fluid from between the bones in your lower spine. You usually go home the same day.
Will I need to do anything to prepare for the test?
For blood and urine tests, there are no special preparations.
For a CSF analysis (spinal tap), you may be asked to empty your bladder (pee) and bowels (poop) before the test.
Are there any risks to the test?
With a blood test, there is very little risk. After the test, you may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
With a urine test, there is no known risk.
With a CSF analysis, there is very little risk from a spinal tap. You may feel a little pinch or pressure when the needle is inserted. After the test, you may feel some pain or tenderness in your back or have some bleeding where the needle was inserted. You may also get a headache. The headache may last for several hours or up to a week or more. Your provider may suggest treatment to relieve the pain.
What do the results mean?
If your B2M levels were measured to learn about your cancer:
- The higher your B2M levels, the more cancer you have in your body. Higher levels are linked to cancers that tend to grow faster./li>
- If you have multiple myeloma, higher levels of B2M are linked with kidney problems.
If your B2M levels were measured to check how well your treatment is working, your provider may look at several test results over time to look for a trend:
- Increasing B2M levels may mean your treatment is not working.
- Decreasing B2M levels may mean your treatment is working.
- B2M levels that don’t change may mean that your disease is stable and hasn’t gotten better or worse.
If you have questions about your test results, talk with your provider.
Is there anything else I need to know about a beta-2 microglobulin tumor marker test?
B2M levels may be higher than normal in many conditions that aren’t cancer. The amount of B2M in body fluids may be measured in conditions such as:
Courtesy of MedlinePlus from the National Library of Medicine.