Serum or Plasma Concentration of Kappa Light Chain (Free)

What This Test Measures

Free kappa light chains are part of the larger antibody proteins, which the immune system uses to fight infections. When antibodies break down, their light chains can be released into the bloodstream. This test specifically looks at the free (unattached) kappa light chains, which can be elevated in conditions like multiple myeloma, lymphoma, or other cancers that involve abnormal antibody production.

Why It Might Be Ordered

Your doctor may order this test to investigate symptoms like unexplained fatigue, bone pain, frequent infections, or kidney problems. It’s also used as part of a broader evaluation for blood cancers or to monitor treatment progress in patients already diagnosed with certain cancers.

Common Conditions Monitored

High levels of free kappa light chains can signal conditions such as multiple myeloma (a cancer of plasma cells), Waldenström macroglobulinemia (a type of lymphoma), or other monoclonal gammopathies (abnormal protein accumulations). Low or normal levels are generally not concerning unless part of a broader diagnostic workup.

Sample Collection and Preparation

This test requires a blood sample drawn from a vein in your arm. The blood is typically processed into either serum (after clotting) or plasma (after anticoagulation) and sent to a lab for analysis. You may be asked to fast before the test, depending on your doctor’s instructions.