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Health Library

Free Light Chains (Blood)

Does this test have other names?

Serum free light chain assay, Freelite

What is this test?

This test looks for signs of antibodies called immunoglobulins in your blood.

Immunoglobulins are made by white blood cells called plasma cells to help protect you against infection and illness. Plasma, or myeloma, cells are found in your bone marrow. Light chains, also called Bence Jones proteins, make up part of the structure of immunoglobulins. Immunoglobulins are also made up of heavy chains.

The light chains attach themselves to the heavy chains and are then called bound light chains. When you have more light chains than heavy chains, those extra light chains are called "free" because they don't bind to the heavy chains. Instead, they are released in the blood. The more free light chains in your blood, the more plasma cells you have, which may mean there is a problem with the plasma cells.

This test is used to help diagnose a type of cancer called multiple myeloma. It may also be used to diagnose other conditions affecting the cells in your bone marrow, including a usually benign condition called monoclonal gammopathy of undetermined significance, or MGUS, and a serious disease called amyloidosis.

Why do I need this test?

You may need this test if your doctor suspects a problem with your plasma cells or multiple myeloma. You may not have signs and symptoms, but if you do, they may include:

  • Pain in your bones

  • Increased protein on a blood test

  • Anemia, or a low red blood cell count

  • Hypercalcemia, or high levels of calcium in the blood

  • Kidney problems

  • Skin rash

  • Nerve damage

  • Inflammation in the blood vessels called vasculitis

What other tests might I have along with this test?

Your doctor may also order other tests, including:

  • Biopsy of your bone marrow

  • Electrophoresis tests of proteins in your blood

  • Electrophoresis tests of proteins in your urine

  • Free light chain test of your urine

  • Immunoglobulin test on your blood

  • Bone imaging tests

  • Other blood tests, including complete blood count, creatinine, and calcium

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

Results are given in milligrams per liter (mg/L). The test measures the levels of specific types of free light chains, known as kappa and lambda, and also the ratio between the two. Normal test results for free light chains are:

  • 3.3 to 19.4 mg/L kappa free light chains

  • 5.71 to 26.3 mg/L lambda free light chains

  • 0.26 to 1.65 ratio of kappa/lambda

If your results are higher or lower, it may mean you have a problem with your plasma cells, such as multiple myeloma.

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.

What might affect my test results?

Other factors aren't likely to affect your results.

How do I get ready for this test?

You don't need to prepare for this test. But be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use. 

Free Light Chains (Blood) - WellSpan Health

Author: Rodriguez, Diana
Online Medical Reviewer: Hanrahan, Maura, MD
Online Medical Reviewer: Sohrabi, Farrokh, MD
© 2014 WellSpan Health. All Rights Reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.

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