Do patients with MGUS require a bone marrow biopsy?

Abstract

8117 Monoclonal gammopathy of undetermined significance (MGUS) increase in prevalence with age and it is associated with risk of progression to plasma cell disorder. According to ASH guidelines, patients (pts) should have a complete blood count (CBC), creatinine, calcium, and a complete bone survey and periodic follow up. There has been no clear-cut guideline regarding the role of bone marrow biopsy in these patients. There is suggestion in the literature that bone marrow aspiration and biopsy is indicated if the M protein is 1.5 g/dL. Hypothesis We hypothesize that the increase in serum immunoglobulin is correlated with an increase in plasma cell in the bone marrow biopsy. Methods: We performed a retrospective chart review of 327 MGUS veteran patients seen from 2002 to 2005. Diagnostic criteria for MGUS were defined as <3 g/dL serum monoclonal protein, <10 % plasma cells in the bone marrow and absence of radiographic or laboratory abnormality related to the plasma cell proliferative process. Patients with smoldering myeloma were excluded. Bone marrow biopsies were available on 97/327 patients. Bone marrow biopsy with plasma cell percentage, serum protein electrophoresis (SPEP) and immunofixation (SFE), and immunoglobulin levels of these patients were retrieved and statistical analysis was performed by using Pearson correlation coefficient and linear regression analysis to detect the correlation between plasma cell percentage and immunoglobulin levels. Results: Of the 97 patients whom the bone marrow biopsy was available, 66 patients had IgG, 15 had IgA and 16 had IgM monoclonal paraprotein. There was linear correlation between serum IgG and IgA levels with the percentage of plasma cells in the bone marrow. (p< 0.001 and < 0.02 respectively. By regression analysis, using a cut off value of 10% plasma cells in the bone marrow, the predicted level of IgG and IgA immunoglobulin was 2124 mg /dl and 1564 mg/dl respectively. There was no correlation between IgM immunoglobulin and plasma cell percentage in the marrow. Conclusion: There is a linear correlation between serum IgG and IgA immunoglobulin with plasma cell percentage in the bone marrow. Bone marrow biopsy with plasma cell percentage of 10% or higher may be predicted in patients with MGUS with IgG or IGA above 2g/dl and 1.5g/dl respectively. No significant financial relationships to disclose.