Aspetti metodologici nella ricerca e caratterizzazione delle componenti monoclonali nel siero

Serum protein electrophoresis (SPE) is a screening test widely used in clinical practice to identify patients with monoclonal gammopathies. SPE, performed on agarose gel (AGE) or by capillary zone electrophoresis (CZE), is the only technique able to recognize a monoclonal immunoglobulin. To detect monoclonal components (MC), SPE must be visually inspected. The two available techniques show similar sensitivity for MC detection (CZE 95%, AGE 91%), with a higher specificity for AGE (99% vs. 78% for CZE). Any MC detected must be reported, because also small B-cell clones could be dangerous. Once detected, MCs need to be quantitatively measured directly on the SPE pattern by setting the limits of the corresponding peak. A concentration-related bias in MC quantitation between AGE and CZE exists. Immunotyping is the further mandatory test for confirmation and characterization of MC by either immunofixation (IFE) or immunosubtraction (ISE). In general, IFE is more sensitive than ISE, but high resolution (HRIFE) must be warranted. However, ~25% of IFE carried out on commercially available kits are difficult to interpret and thus not reportable. For identification of amyloidogenic light chain MC, sensitivity of the manual HR-IFE is 95% vs. 80% of conventional semiautomated assays. The recently introduced quantitative serum assay for immunoglobulin free light chains (FLC) is an accurate index of clonality, particularly for FLC myeloma and AL amyloidosis. To reach the highest sensitivity in MC detection a comprehensive screening panel including SPE, HR-IFE and FLC determination is recommended.