Bone-marrow immunophenotypic analysis allows the identification of high risk of progression and immune condition-related monoclonal gammopathy of undetermined significance.

Background: Monoclonal gammopathy of undetermined significance (MGUS) progresses to plasma cell dyscrasia at a rate of 1% per year. A high prevalence of MGUS has been noted in series of patients with immune disorders or chronic infections.

Methods: Retrospective cohort and a cross-sectional study to analyze the prognostic value of aberrant (CD38(+ +)CD138(+) CD19(-)CD45(weak)) to normal phenotype (CD38(+ +)CD138(+) CD19(+)CD45(+)) bone-marrow plasma cells ratio (A/N ratio) for the development of a plasma cell dyscrasia and the association with the presence of a chronic immune disorder.

Results: A total of 322 patients were included with a median follow-up of 46 months. Analysis for progression revealed an increased A/N ratio as the main independent prognostic variable. A significant association between a reduced A/N ratio and the diagnosis of a chronic immune condition was found. Using receiver-operating characteristic analysis we created an A/N ratio range from 4 to 0.20. Values of 4 or higher define a group at high risk of progression (OR 10.7). A/N values of 0.20 or lower are associated with immune disorders or chronic infections (OR 20.9).

Conclusions: Extreme values of the A/N ratio seem to be related with two different conditions: high risk of progression, and immune condition-related MGUS.