Serum or Plasma Free Light Chain Kappa to Lambda Ratio (Free Light Chain Ratio)

Why This Test Matters

Light chains are small protein fragments produced by plasma cells, which are a type of white blood cell. When these cells become abnormal (as in multiple myeloma or other disorders), they may produce an excess of either kappa or lambda light chains. Measuring their balance helps identify imbalances that may signal disease.

What to Expect During the Test

A blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab where the light chains are separated and measured. No special preparation is needed, but fasting may be advised depending on your doctor’s instructions.

Common Conditions Monitored

This test is often used to detect or monitor conditions like multiple myeloma, monoclonal gammopathy of undetermined significance (MGUS), and other plasma cell disorders. It can also help track treatment progress or response to therapy.

How the Results Are Used

Your doctor may use the free light chain ratio to diagnose conditions where plasma cells are abnormal, check for disease progression, or evaluate treatment effectiveness. Results are compared to your baseline or to other lab values for context.