Diagnostic value of laboratory methods of paraprotein evaluation for diagnosis of monoclonal gammmopathy
Electrophoresis with immunofixation is a sensitive technology for paraprotein (PP) detection and characterization in monoclonal gammopathies (MG). Immunometric measurement of immunoglobulin free light chains (FLC) is an alternative method to estimate PP clonality. This method is based on light chain restriction phenomenon in monoclonal synthesis, which leads to absolute or relative change of FLC level. Recently, FLC ratio in blood serum was recommended as a standard test for MG screening and monitoring. To compare efficacy of FLC measurement and immunofixation electrophoresis for MG diagnostics we studied 89 healthy donors and 165 MG patients. We performed immunofixation electrophoresis in all sera by electrophoresis hardware and reagents (Helena Biosciences, England). We detected serum FLC levels by commercial ELISA kit (Polyg-nost, Russia). The reference values for kappa-FLC serum concentrations were 3.25-15.81 yg/mL, for lambda-FLC: 3.23-28.05 yg/mL, and for kappa to lambda ratio: 0.3-1.9. An absolute increase of kappa-FLC was found in 67.68 % (67 of 99) and kappa to lambda ratio increase in 62.63 % (62 of 99) cases with PP, containing kappa-FLC (p < 0.01). An increase of lambda-FLC was found in 69.7 % (46 of 66), and decrease of kappa to lambda ratio was in 80.3 % (53 of 66) cases with PP, containing lambda-FLC. Thereby, it is not possible to identify all patients with MG by the use of FLC measurement only. At the same time, immunofixation in some cases also fails to give complete information. So we recommend the combination of FLC measurement with ratio calculation and immunofixation for highly sensitive laboratory detection of MG.