Free light chain test

 

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
• Fatigue
• 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
• Amyloidosis
• 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 should know?Monoclonal gammopathy of undetermined significance (MGUS) is the most common plasma cell disorder and it usually does not cause symptoms. A minority of people with MGUS will later develop multiple myeloma. This risk is increased in those with increased free light chain production and an abnormal kappa/lambda ratio.

Serum free light chains can also be increased, usually with a normal kappa/lambda ratio, with some connective tissue disorders, inflammatory conditions, neurological conditions, and some cancers but are not typically monitored in people with these conditions.

Serum free light chain analysis accelerates the detection of treatment response because the free light chains have a much shorter half-life (3-5 hours) than intact immunoglobulins (about 21 days). Although it is traditionally used for light chain-only plasma cell disorders, the test is also used for assessing response and minimal residual disease in myelomas that produce intact immunoglobulins.

If someone has this testing done at more than one laboratory, the results may not be interchangeable if the laboratories use different testing methods. If you are having a series of SFLC tests done, it is advised that you have the tests done by the same method, typically by the same laboratory, so that the results can be compared and interpreted correctly. You may wish to discuss this issue with your health care practitioner.

 the effectiveness of treatment.

What does the test result mean?

This test must be interpreted in conjunction with other laboratory and clinical findings. A slightly abnormal result does not prove that someone has a plasma cell disorder. Conversely, someone may have a plasma cell disorder despite a normal result from this test. If a person has a plasma cell disorder, the result of this test won’t indicate what specific plasma cell disorder is present.

Results of a serum free light chain test will often be evaluated in conjunction with the results of a protein electrophoresis test.

Free light chains will normally be present in the blood at low levels, with a kappa/lambda ratio of approximately 0.26 to 1.65 for individuals with normal kidney function.

Increased kappa free light chains and an increased kappa/lambda ratio may be seen with plasma cell disorders that produce excess monoclonal kappa light chains. Increased lambda free light chains and a decreased kappa/lambda ratio may be seen with plasma cell disorders that produce excess monoclonal lambda light chains.

In the context of MGUS or myeloma, significantly increased free light chain production and a markedly abnormal kappa/lambda ratio indicate an increased risk of disease progression.

When the test is used to monitor a known plasma cell disorder, a decrease in the quantity of excess light chain and a more normal kappa/lambda ratio may indicate a response to treatment.

Increased free light chains and/or an abnormal serum free kappa/lambda ratio may be seen with people who have some degree of kidney dysfunction that is unrelated to a plasma cell disorder. Decreased free light chains with a normal kappa/lambda ratio may be seen with a disorder that suppresses bone marrow cell production.

With suspected primary amyloidosis, an increase in serum free light chains with an abnormal kappa/lambda ratio may suggest that amyloidosis is the cause of symptoms. However, a biopsy of affected tissue establishes the diagnosis.What is primary amyloidosis?

Amyloidosis is a condition that occurs when abnormal proteins, called amyloids, are produced and deposited in various organs in the body, causing tissue and organ damage. This is a rare, progressive disorder that can affect one or more organs, including the heart, liver, kidneys and gastrointestinal tract.

The amyloidosis disorders can be divided by types of amyloid protein, primary (clonal) versus secondary (reactive), and acquired versus hereditary. Primary amyloidosis is the most common form and is sometimes seen in association with MGUS or multiple myeloma. It results from the deposition of whole or fragments of immunoglobulin light chains (known as AL amyloid) secreted by clonal plasma cells into various organs and tissues. The deposition of this material typically results in organ dysfunction