Serum Total Protein and Albumin-to-Globulin Ratio in Multiple Myeloma
In multiple myeloma, total protein is typically elevated (often >8 g/dL, with 30% of patients showing hyperproteinemia), while the albumin-to-globulin (A/G) ratio is characteristically low (reversed), with 54% of patients presenting with a low A/G ratio at diagnosis. 1
Total Protein Findings
Hyperproteinemia occurs in approximately 30% of newly diagnosed multiple myeloma patients, reflecting the overproduction of monoclonal immunoglobulins by malignant plasma cells 1
The elevated total protein results from increased globulin fraction (specifically the monoclonal protein), while albumin levels are typically normal or decreased 1
Serum protein electrophoresis reveals a localized M-band in 70.8% of patients, with 78% migrating to the γ-region and 18% to the β-region 1
Albumin-to-Globulin Ratio Characteristics
The A/G ratio is reversed (low) in 54.2% of multiple myeloma patients at diagnosis, making it a valuable diagnostic marker 1
The A/G ratio demonstrates high diagnostic accuracy with an AUC of 0.910 for diagnosing multiple myeloma, showing the highest sensitivity among protein markers 2
An optimal cutoff of AGR ≤1.16 identifies patients with worse prognosis, as low AGR independently predicts inferior overall survival (HR=1.82) and progression-free survival (HR=1.53) 3
Clinical Significance and Diagnostic Value
The reversed A/G ratio results from two mechanisms: decreased albumin production (related to tumor burden and disease stage) and increased globulin from monoclonal protein production 4
Hypoalbuminemia correlates significantly with disease stage, tumor burden, and monoclonal IgG levels, with albumin ≤29 g/L identifying advanced disease and virtually all stage III patients having albumin ≤37 g/L 4
The A/G ratio effectively differentiates multiple myeloma from other conditions causing protein abnormalities, with AUC of 0.884 for distinguishing MM from liver disease and 0.905 for distinguishing MM from kidney disease 2
Important Caveats
Light chain multiple myeloma patients may present with normal A/G ratio despite having elevated α2-globulin concentration, as light chains are not adequately captured by standard protein electrophoresis 1
Approximately 4% of patients have non-secretory myeloma where standard protein measurements may be normal, requiring serum free light chain assays for diagnosis 1
The presence of anemia, high ESR, and low A/G ratio in elderly patients should prompt immediate investigation for multiple myeloma, as these findings together are highly suggestive of the disease 1
Both serum protein electrophoresis and nephelometric quantification should be performed, as they are complementary tests recommended by the International Myeloma Workshop 5