Evaluation of routine laboratory parameters as clinical indicators of disease severity in multiple myeloma

INTRODUCTION: Multiple myeloma (MM) is characterized by clonal plasma cell proliferation and significant systemic im-pacts. This study aimed to evaluate the relationship between routine hemogram and biochemical parameters and disease severity markers (M-protein and β-2 microglobulin [β-2M]) to identify accessible clinical indicators of tumor load at the time of diagnosis.
METHODS: In this retrospective cross-sectional study, newly diagnosed, treatment-naive MM patients and healthy con-trols were analyzed. Statistical significance was set at a threshold (p<0.00125) using Bonferroni correction to prevent Type I errors. Multivariable logistic regression was performed to identify independent predictors of high M-protein load (≥3g/dL), and ROC analysis was used to determine the diagnostic performance of significant parameters.
RESULTS: MM patients exhibited significantly lower WBC, RBC, HCT, and PLT counts, and higher BUN and CRP levels compared to controls (p<0.001). β-2M showed significant correlations with several routine parameters; however, partial correlation and multivariable regression revealed that these associations were entirely dependent on renal function. Conversely, multivariable logistic regression identified RBC count (OR=0.383, p=0.026), eGFR, and age as significant in-dependent predictors of high M-protein load. Notably, each 1×10⁶/μL decline in RBC count was associated with a 161% increase in the risk of high disease severity. ROC analysis established an optimal RBC cut-off value of 3.73×10⁶/μL (AUC: 0.695, sensitivity: 64.1%, specificity: 69.6%) for predicting high tumor load.
DISCUSSION AND CONCLUSION: Routine laboratory data, particularly RBC count, serve as powerful indicators of MM severity at the time of initial diagnosis. Unlike β-2M, which is heavily influenced by renal status, RBC count is an independent predictor of monoclonal protein load. A baseline RBC level below 3.73×10⁶/μL should alert clinicians to a potentially high tumor load, facilitating rapid triage and treatment prioritization.

Keywords: Beta 2-microglobulin, complete blood count, C-reactive protein, multiple myeloma, paraproteins