Kappa/lambda ratio on peripheral blood lymphocytes and bone marrow plasma cell labeling index in monoclonal gammopathies.

Bone marrow plasma cell labeling index (L.I.), kappa/lambda ratio, CD4+ and CD8+ subpopulations were studied in patients with smoldering multiple myeloma (SMM), active myeloma (MM) and monoclonal gammopathy of undetermined significance (MGUS). The loss of the light chain isotype suppression (LCIS) and a high labeling index (L.I.) allowed us to distinguish all MM patients from SMM patients. On the contrary, a low L.I. and a normal kappa/lambda ratio were found in most kappa and lambda MGUS. A significant difference in the kappa/lambda ratio was noted between MGUS and K-SMM. A significant decrease in CD4+ and a significant increase in CD8+ were not observed in patients with LCIS. The kappa/lambda ratio together with the plasma cell L.I. could be useful parameters for distinguishing active MM from SMM, especially in the cases with a border line L.I.