What is a beta-2 microglobulin tumor marker test?
This test measures the amount of a protein called beta-2 microglobulin (B2M) in the blood, urine, or cerebrospinal fluid (CSF). B2M is a type of tumor marker. Tumor markers are substances made by cancer cells or by normal cells in response to cancer in the body.
B2M is found on the surface of many cells and is released into the body. Healthy people have small amounts of B2M in their blood and urine.
- People with cancers of the bone marrow and blood often have high levels of B2M in their blood or urine. These cancers include multiple myeloma, lymphoma, and leukemia.
- High levels of B2M in cerebrospinal fluid can mean that cancer has spread to the brain and/or spinal cord.
A B2M tumor marker test is not used to diagnose cancer. But it can provide important information about your cancer, including how serious it is and how it may develop in the future.
Other names: total beta-2 microglobulin, β2-microglobulin, B2M
What is it used for?
A beta-2 microglobulin tumor marker test is most often given to people who have been diagnosed with certain cancers of the bone marrow or blood. The test may be used to:
- Figure out the severity of cancer and whether it has spread. This process is known as cancer staging. The higher the stage, the more advanced the cancer is.
- Predict disease development and guide treatment.
- See if cancer treatment is effective.
- See if cancer has spread to the brain and spinal cord.
Why do I need a beta-2 microglobulin tumor marker test?
You may need this test if you have been diagnosed with multiple myeloma, lymphoma, or leukemia. The test can show the stage of your cancer and whether your cancer treatment is working.
What happens during a beta-2 microglobulin tumor marker test?
A beta-2 microglobulin test is usually a blood test, but may also be given as a 24-hour urine test, or as 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, your health care provider or a laboratory professional will give you a container to collect your urine and instructions on how to collect and store your samples. A 24-hour urine sample test usually includes the following steps:
- Empty your bladder in the morning and flush that urine away. Record the time.
- For the next 24 hours, save all your urine in the container provided.
- Store your urine container in the refrigerator or a cooler with ice.
- Return the sample container to your health provider’s office or the laboratory as instructed.
For a cerebrospinal fluid (CSF) analysis, a sample of spinal fluid will be collected in a procedure called a spinal tap (also known as a lumbar puncture). A spinal tap is usually done in a hospital. During the procedure:
- You will lie on your side or sit on an exam table.
- A health care provider will clean your back and inject an anesthetic into your skin, so you won’t feel pain during the procedure. Your provider may put a numbing cream on your back before this injection.
- Once the area on your back is completely numb, your provider will insert a thin, hollow needle between two vertebrae in your lower spine. Vertebrae are the small backbones that make up your spine.
- Your provider will withdraw a small amount of cerebrospinal fluid for testing. This will take about five minutes.
- You’ll need to stay very still while the fluid is being withdrawn.
- Your provider may ask you to lie on your back for an hour or two after the procedure. This may prevent you from getting a headache afterward.
Will I need to do anything to prepare for the test?
You don’t need any special preparations for a blood or urine test.
You don’t need any special preparations for a CSF analysis, but you may be asked to empty your bladder and bowels before the test.
Are there any risks to the test?
There is very little risk to having a blood or urine test. After 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.
There is very little risk to having a spinal tap. You may feel a little pinch or pressure when the needle is inserted. After the test, you may get a headache, called a post-lumbar headache. About one in ten people will get a post-lumbar headache. This can last for several hours or up to a week or more. If you have a headache that lasts longer than several hours, talk to your health care provider. He or she may be able to provide treatment to relieve the pain. You may feel some pain or tenderness in your back at the site where the needle was inserted. You may also have some bleeding at the site.
What do the results mean?
If the test was used to find out how advanced your cancer is (cancer stage), the results may show how much cancer is in your body and whether it is likely to spread.
If the B2M test was used to check how well your treatment is working, your results may show:
- Your B2M levels are increasing. This may mean your cancer is spreading, and/or your treatment is not working.
- Your B2M levels are decreasing. This may mean your treatment is working.
- Your B2M levels have not increased or decreased. This may mean your disease is stable.
- Your B2M levels decreased, but then later increased. This may mean your cancer has come back after you’ve been treated.
If you have questions about your results, talk to your health care provider.
Is there anything else I need to know about a beta-2 microglobulin tumor marker test?
Beta-2 microglobulin tests are not always used as tumor marker tests for cancer patients. B2M levels are sometimes measured to:
- Check for kidney damage in people with kidney disease.
- Find out if a viral infection, such as HIV/AIDS, has affected the brain and/or spinal cord.
- Check to see if disease has advanced in people with multiple sclerosis, a chronic disease affecting the brain and spinal cord.