From the Guidelines
An IgG level of ≥3 g/dL is concerning for multiple myeloma, particularly in the context of smoldering or active myeloma. This threshold is based on the National Comprehensive Cancer Network (NCCN) clinical practice guidelines in oncology, version 3.2017 1. According to these guidelines, smoldering (asymptomatic) myeloma is defined by serum monoclonal protein IgG or IgA ≥3 g/dL, among other criteria. It's essential to note that the diagnosis of multiple myeloma requires a comprehensive evaluation, including the presence of clonal bone marrow plasma cells, myeloma-defining events, and other diagnostic criteria.
Key points to consider in the diagnosis of multiple myeloma include:
- Serum monoclonal protein levels (IgG or IgA ≥3 g/dL)
- Clonal bone marrow plasma cells (≥10% or biopsy-proven bony or extramedullary plasmacytoma)
- Myeloma-defining events, such as hypercalcemia, renal insufficiency, anemia, or bone lesions
- Abnormal serum free light chain ratio (≥100 or ≤0.01)
- More than one focal lesion on MRI studies
The pattern of IgG elevation (monoclonal vs. polyclonal) is more significant than the absolute value, and a monoclonal spike on serum protein electrophoresis with immunofixation confirming IgG type provides stronger evidence for myeloma than total IgG levels alone. Elevated IgG levels should be evaluated in the context of these diagnostic criteria to determine the risk of progression to active myeloma [1, @2@].
From the Research
Concerning IGG Levels for Myeloma
- The concerning IGG level for myeloma is not explicitly stated in the provided studies, but study 2 suggests that an IgG level greater than 64 g/L is a poor prognostic factor affecting progression-free survival (PFS) and overall survival (OS) in patients with IgG-type multiple myeloma.
- Study 3 found that the combination of serum IgG, κ light chain, λ light chain, C3, and C4 levels can be more effective than any single indicator in efficacy evaluation of bortezomib treatment for multiple myeloma.
- Study 4 showed that high IgG levels at initial diagnosis are associated with shorter recurrence time after initial treatment in patients with IgG-type multiple myeloma.
Prognostic Factors
- High IgG levels (>64 g/L) are associated with poor prognosis, including shorter PFS and OS, as well as higher risk of high-risk cytogenetics (HRC) 2.
- Low serum albumin levels are independently correlated with high IgG levels in IgG-type multiple myeloma patients at initial diagnosis 4.
- High levels of bone marrow plasma cells, lactate dehydrogenase, creatinine, β2-microglobulin, and IgG, as well as low levels of hemoglobin and serum albumin, are associated with shorter recurrence time after initial treatment 4.