Detection and Characterization of Monoclonal Components in Serum and Urine (Editorial‪)‬

Detection of a monoclonal component (the immunoglobulin product of a clone of plasma cells) in the serum and/or urine is an important part of the laboratory evaluation of a patient with a plasma cell or B-lymphocyte proliferative disease. Usually, large quantities of monoclonal components are present in the serum of patients with multiple myeloma or Waldenstrom's macroglobulinemia. Small quantities of monoclonal components in serum may signify light chain disease, a B-lymphocytic lymphoma or leukemia, amyloid AL (amyloidosis associated with immunoglobulin light chains), a neuropathy, or the predisposition to develop a malignant plasma cell/B-lymphocyte proliferative disorder in a patient with no currently evident clinical problem (monoclonal gammopathy of undetermined significance-MGUS). About 25% of individuals who fall into the MGUS category develop myeloma or a related B-lymphocyte proliferative disorder after 20 to 35 years of follow-up (1). Because of this, annual follow-up is prudent, even for patients with relatively small monoclonal components in their serum. For the past half-century, protein electrophoresis using either cellulose acetate or agarose gels has been the mainstay in screening serum and urine for monoclonal components. Most of the currently used electrophoretic techniques require a considerable amount of manual labor. Thus, although the reagents are relatively inexpensive, the time involved in applying the samples, fixing, staining, and washing the gels, and performing the densitometric scans of the gels make electrophoresis rather costly. Furthermore, there is considerable variation in the resolution of the major protein fractions from one manufacturer's product to another. Some relatively simple and inexpensive techniques allow one to recognize only five bands that often have fuzzy borders. Those techniques make it difficult to detect small monoclonal components or those that migrate in the beta region, where transferrin, C3, and (3-lipoprotein may obscure a subtle monoclonal band. Not surprisingly, techniques that provide a high-resolution electrophoretic pattern with crisp resolution of the beta region bands are more complex and costly than the five-band techniques. The degree of resolution to optimize detection of quantitatively small monoclonal components or those with migration in the alpha, beta, or extreme slow gamma regions remains controversial. Objective data on the issue of resolution and detection of monoclonal components is sparse. However, some quality-assurance survey results suggest that gels capable of providing a distinct separation of transferrin (beta 1 region) from C3 (beta 2 region) may facilitate detection of subtle monoclonal components (2).