The aim of the presented study is to display general information about the clinical significance of quantitative assessment of serum free light chains (S-FLC) of immunoglobulins and their mutual ratio (index κ/λ) in individual forms of monoclonal gammopathies (MG). The study describes methodical aspects of automatic quantitative immunochemical analysis using high avidity polyclonal antibody against the internal epitope of the molecules of LC κ and λ enabling reliable detection of FLC. It also demonstrates the fundamental contribution of assessment of S-FLC and the κ/λ index for the diagnostics of Bence-Jones, non- and hyposecretory and IgD multiple myeloma, and also for continual evaluation of the course of the disease, depth of therapeutic response, duration of stable/plateau phase, for early recognition of relapse/progression and therapy resistance as well as the assessment of the depth of therapeutic response (stringent complete remission, sCR) in all forms of MM. We also describe the significance for the diagnostics and evaluation of therapeutic response in systemic AL-amyloidosis, primary macroglobulinemia and solitary plasmocytoma, we also discuss the contribution for evaluation of monoclonal gammopathy of undetermined significance including its stratification to three groups (low, intermediate and high risk) with different prognosis. The presented study concludes that the introduction of this modern immunochemical method enabling the quantification of S-FLC makes the way for new clinical applications, especially for more precise recognition and monitoring of the course of practically all types of MG.

        Key words: free light chains of immunoglobulins, automatic immunochemical analysis, monoclonal gammopathy, Bence-Jones myeloma, non-secretory myeloma, AL-amyloidosis, primary macroglobulinemia, monoclonal gammopathy of undetermined significance.