What is a free light chains test?
Light chains are proteins made by plasma cells, a type of white blood cell. Plasma cells also make immunoglobulins (antibodies). Immunoglobulins help protect the body against illness and infections. Immunoglobulins are formed when light chains link up with heavy chains, another type of protein. When light chains link up with heavy chains, they are known as bound light chains.
Normally, plasma cells make a small amount of extra light chains that don't bind with heavy chains. They are instead released into the bloodstream. These unlinked chains are known as free light chains.
There are two types of light chains: lambda and kappa light chains. A free light chains test measures the amount of lambda and kappa free light chains in the blood. If the amount of free light chains is higher or lower than normal, it can mean you have a disorder of the plasma cells. These include multiple myeloma, a cancer of plasma cells, and amyloidosis, a condition that causes a dangerous buildup of proteins in different organs and tissues.
Other names: free kappa/lambda ratio, kappa/lambda quantitative free light, freelite, kappa and lambda free light chains, immunoglobulin free light chains
What is it used for?
A free light chains test is used to help diagnose or monitor plasma cell disorders.
Why do I need a free light chains test?
You may need this test if you have symptoms of a plasma cell disorder. Depending on which plasma disorder you may have and which organs are affected, your symptoms may include:
- Bone pain
- Numbness or tingling in arms and legs
- Tongue swelling
- Purple spots on the skin
What happens during a free light chains 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.
Will I need to do anything to prepare for the test?
You don't need any special preparations for a free light chains test.
Are there any risks to a free light chains 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.
What do the results mean?
Your results will show amounts for lambda and kappa free light chains. It will also provide a comparison between the two. If your results were not normal, it may mean you have a plasma cell disorder, such as:
- Multiple myeloma
- MGUS (monoclonal gammopathy of unknown significance). This is a condition in which you have abnormal protein levels. It often causes no problems or symptoms, but sometimes it develops into multiple myeloma.
- Waldenstrom macroglobulinemia (WM), a cancer of the white blood cells. It's a type of non-Hodgkin lymphoma.
Is there anything else I need to know about a free light chains test?
A free light chains test is often ordered with other tests, including an immunofixation blood test, to help confirm or rule out a diagnosis.
- American Cancer Society [Internet]. Atlanta: American Cancer Society Inc.; c2019. Tests to Find Multiple Myeloma; [updated 2018 Feb 28; cited 2019 Dec 21]; [about 4 screens]. Available from: https://www.cancer.org/cancer/multiple-myeloma/detection-diagnosis-staging/testing.html
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