Each antibody (immunoglobulin) used to defend against infection and other aggressions consists of a pair of heavy chains (G, A, M) and a pair of light chains (kappa or lambda). Normally, plasmocytes (white cells) make complete antibodies with the kappa and lambda chains in roughly equal amounts (kappa/lambda ratio between 0.3 and 1.6). In some plasmocyte anomalies (monoclonal gammopathy), the production of one of the two chain subtypes is increased. The free ka/la index (CLL, CLLS, kappa and lambda light chains, free light chain testing and ratio) will then be unusually high (excess kappa chains) or very low (excess lambda chains). The measurement of the ka/la index (CLL, CLLS, kappa and lambda light chains, free light chain testing and ratio) is most often performed following the discovery of a monoclonal-looking anomaly in the protein electrophoresis and immunofixation. In some cases, even in the absence of an electrophoresis anomaly, there may be an abnormal production of free chains.
In the appropriate clinical context, a ka/la index (CLL, CLLS, kappa and lambda light chains, light chain testing and ratio) that is far from normal values is compatible with multiple myeloma. The more abnormal the index, the greater the risk of disease progression. An abnormal ratio can also be caused by kidney malfunction. Low levels of kappa and lambda fractions with a normal index can be caused by any condition that interferes with the production of bone marrow cells.