Serum κand λ-free light chains and its ratio were measured in 126 patients 23-80 years old with monoclonal gammapathies and 60 normal individuals 25-82 years old. The diagnosis were intact immunoglobulin multiple myeloma (IIMM) ( n = 87), Bence Jones myeloma ( n = 18), nonsecretory MM ( n = 7), plasmоcytoma ( n = 6) and monoclonal gammapathies of undetermined significance (MGUS) ( n = 8). The FLCs assay was performed using the Freelite TM assay (The Binding Site Ltd, UK) on a Hitachi 911 automated nephelometer. Three serum preparation containing different levels of κ-FLC and λ-FLC were assayed. The precision of the FLCs assays was good with percentage coefficients of variation less than 10 %. Free lite chains immunoassay represents a greater than 100-fold increase in analytical sensitivity compare to electrophoresis methods for the detection of FLC. sFLC levels were found to be high in most patients with IIMM, Bence Jones myeloma and plasmоcytoma. The diagnostic accuracy of FLC assay in serum by immunoturbidimetry method was 90.5 %. Combining sFLC testing with serum protein electrophoresis and immunofixation provides 98.8 % accuracy in the first-line diagnosis of monoclonal gammapathies. Our study demonstrated high specificity, assay and diagnostic sensitivity for immunoturbidimetry method detection of FLC in serum.

Data on comparative analysis of concentration of κand λ-free light chains (FLC) of immunoglobulines and their ratios in blood serum of 74 patients with monoclonal gammapathy and practically healthy 60 people have been presented. The increase in serum FLC concentration is most frequent for patients with multiple myeloma, plural myeloma Bens-Johns and monoclonal gammapathy of unclear genesis, mainly at the expense of increased κ-FLC concentration. Concentration of κ-FLC and λ-FLC in blood of patients essentially decreased after the reaching of partial or full remission, and again increased after the relapse of the basic disease or remained practically at initial level at inefficiently treated patients. The immunoturbidimetriya method of FLC determination in blood serum in comparison with standard electrophoresis methods differed by more analytical sensitivity with a detection threshold of κ-FLC 1,5 mg/l and λ-FLC 3 mg/l. Diagnostic sensitivity of FLC determination in patients blood serum by immunoturbidimetric method reached 91,7 %. The combination of the method used by the authors and method of electrophoresis with the subsequent immunofixation of blood serum proteins allowed revealing monoclonal gammapathy in 100 % cases. The received results have shown high analytical and diagnostic sensitivity of the method of FLC determination in blood serum, and also the possibility of carrying out the monitoring of treatment of patients with monoclonal gammapathie.