Serum free light-chain measurement

Immunoglobulin light chains that are circulating in serum in a free (unbound) state are called free light chains (FLCs). Measurement of the serum level of FLCs became practical as a clinical blood test in recent decades. These tests are used as an aid in the diagnosis and monitoring of multiple myeloma and related disorders. There are two types of immunoglobulin light chain produced in humans, designated by the Greek letters kappa (κ) and lambda (λ). Comparing the ratio of κ FLCs to λ FLCs in a person's serum against reference ranges indicates whether that person may have a plasma cell tumour such as multiple myeloma or AL amyloidosis.