Background. The aim of this study was to evaluate significance of CD 38++45-54+, CD 38++45-56+ and CD 38++45-138+ cells counts in peripheral blood of patients with multiple myeloma for monitoring of the minimal residual disease. Methods and Results. A triple-color flow cytometric analysis was used for this purpose. Peripheral blood of 29 patients with multiple myeloma who underwent high dose chemotherapy and autologous stem cells transplantation was repeatedly analysed. Counts of myeloma cells in peripheral blood were compared to serum monoclonal immunoglobulin concentration, serum calcium level, serum C - reactive protein, serum b2microglobulin, and number of myeloma cells in bone marrow (morphology). From 29 patients in this study, 5 patients have relapsed. Patients in relapse had significantly higher counts of CD 38++45-54+, CD 38++45-56+ and CD 38++45-138+ cells in peripheral blood than patients in remission (geometrical average: 12,41; 6,20; 14,45 cells/ ml versus 4,08; 2,87; 2,58 cells/ml). The number of these cells correlated well with serum monoclonal immunoglobulin level and counts of myeloma cells in bone marrow. Conclusion. The authors conclude that the longitudinal multi-color flow cytometric analysis of CD 38++45-54+, CD 38++45-56+ and CD 38++45-138+ cells in peripheral blood of patients with multiple myeloma is a useful method for evaluation of the disease activity. Significance of peripheral myeloma cells count for prediction of the relapse of the multiple myeloma remains to be evaluated.

        Key words: minimal residual disease, multiple myeloma, flow cytometry.