Immunoglobulin free light chain assay using latex agglutination.

Under normal biological conditions, immunoglobulin light chains are generally formed in conjunction with heavy chains; however, small quantities of free light chains are also produced. Thus, two types of immunoglobulin light chains may be identified; immunoglobulin-bound light chains and free light chains. In mature neoplastic B cells, immunoglobulin synthesis, including that of the free light chain, is generally increased. Furthermore, elevated free light chain levels also occur in the presence of renal glomerular and tubular impairment. Thus, the quantitative and qualitative measurement of free light chains is of considerable clinical benefit. Although methods for measurement of free light chains do exist they are technically complicated and time consuming. Previously, we have reported a quantitative nephelometric immunoassay for measuring free light chain levels. We report here a refinement of this method using latex agglutination techniques. This new method enables quantitative measurement of free light chains in serum at levels as low as 1 mg/l and may allow the clinical application of serum free light chain estimation.