All immunoglobulins contain two polypeptide chains: a long (heavy) and a short (light) chain. The two chains interact via disulfide bonds. There are two types of light chains, named kappa and lambda. Serum free light chain (SFLC) testing, a kappa/lambda ratio and a protein electrophoresis test are done to help detect, diagnose and monitor plasma cell disorders (dyscrasias) including multiple myeloma and primary amyloidosis. Normal readings are seen when there is a kappa/lambda ratio of approximately 0.26 to 1.65 and free light chains are present in the blood at low levels. Increased kappa free light chains and an increased kappa/lambda ratio are present with plasma cell disorders that produce excess monoclonal kappa light chains. The tests can also be used to monitor response to treatment. An increase in serum free light chains along with an abnormal kappa/lambda ratio may indicate primary amyloidosis; biopsy of affected tissue is typically used for confirmation of diagnosis. [PMID:6802926 ] [Lab Tests Online:free-light/tab/test] Source: Regenstrief LOINC