Understanding and identifying monoclonal gammopathies.

Monoclonal gammopathies reflect conditions in which abnormal amounts of immunoglobulins are produced by a clone that developed from a single pro-B germ cell. The condition may reflect a disease process or be benign. The primary purpose of this review is to emphasize routine clinical laboratory techniques that currently are recommended for use in identifying monoclonal gammopathies from serum and urine. Selection of the preferred technique and correct interpretation often is dependent on an understanding of the immunological basis and clinical sequelae associated with these conditions. For this reason, we first briefly discuss the structure, production, and nature of immunoglobulins, and then describe important features of the associated diseases. Finally, we discuss strengths and weaknesses of the techniques and make reference to current recommendations to facilitate optimal testing. We discuss in detail high-resolution electrophoresis, methods for quantifying immunoglobulins, immunofixation electrophoresis, problems associated with analysis of urine immunoglobulins, and identification of cryoglobulins and immune complexes.