Background. Monoclonal gammopathies are very heterogenic groups of disorders characterized by the proliferation of a single clone of plasma cells producing amonoclonal immunoglobulin (paraprotein).Monoclonal gammopathies (Kyle) are classified as malignant monoclonal gammopathies and monoclonal gammopathy of the undetermined significance. The prevalence of paraproteinemias is about 1% in people up to the age of 60 and about 10% in persons older than 80 years of age. Methods and Results.We examined blood serumfrom1683 plasma donors (18-60 years) by electrophoretic analysis during the period 1999-2003.We determined monoclonal immunoglobulins in 10 of them (0.6%). The presence of monoclonal gammopathies of undetermined significance was the most frequent (6x), one case was a transient monoclonal gammopathy, two patients were not examined and one patient (46 years old man) had the diagnosis of multiple myeloma. The immunoglobulin class of six paraproteins IgG were observed (4x kappa, 2x lambda), paraprotein IgA was found in two patients (1x kappa, 1x lambda), paraproteinemia IgM-kappa in one patient and double paraproteinemia IgG-kappa + IgA-kappa was proved in another one.M-gradient was determined in nine cases by screening electrophoretic analysis on the agarose gel (SEBIA, France). One M-protein (IgA-lambda) was hidden in beta-globulin region and the diagnosis of multiple myeloma was determined after clinical manifestation this disease. Conclusions. Our study shows, that electrophoretic analysis of serum is necessary to do in all types of blood donors (plasma, blood, thrombocytes). Reliable proof of monoclonal immunoglobulins in blood serum or urine is given only by immunofixation electrophoresis.

        Key words: blood donors and plasma donors, monoclonal gammopathy, monoclonal immunoglobulin, paraprotein, electrophoresis, immunofixation.