From the Guidelines
Multiple myeloma is diagnosed based on the International Myeloma Working Group (IMWG) criteria, which require 10% or more clonal plasma cells in the bone marrow and/or a biopsy-proven plasmacytoma, plus any one or more myeloma-defining events, as outlined in the 2020 Blood Cancer Journal study 1. The diagnostic criteria for Multiple Myeloma (MM) include:
- 10% or more clonal plasma cells in the bone marrow (and/or a biopsy-proven plasmacytoma)
- Plus any one or more myeloma-defining events (MDE), such as:
- End-organ damage (hypercalcemia, renal insufficiency, anemia, or bone lesions) attributable to the underlying plasma-cell disorder
- Bone marrow clonal plasma cells ≥60%
- Serum involved to uninvolved free light chain (FLC) ratio ≥100 (provided involved FLC level is ≥100 mg/L)
- More than 1 focal lesion (5 mm or more in size) on magnetic resonance imaging (MRI) These criteria, as stated in the 2020 study 1, help distinguish active multiple myeloma requiring treatment from precursor conditions like monoclonal gammopathy of undetermined significance (MGUS) or smoldering multiple myeloma. The IMWG diagnostic criteria are essential for accurate diagnosis and treatment of MM, and the presence of any one or more myeloma-defining events, in addition to clonal plasma cells in the bone marrow or a biopsy-proven plasmacytoma, is necessary for a diagnosis of multiple myeloma, as per the 2020 Blood Cancer Journal study 1.
From the Research
Diagnostic Criteria for Multiple Myeloma (MM)
The diagnosis of Multiple Myeloma (MM) requires specific criteria to be met, including:
- ≥10% clonal bone marrow plasma cells or a biopsy-proven plasmacytoma plus evidence of one or more multiple myeloma defining events (MDE) 2, 3, 4
- MDEs include:
- CRAB (hypercalcemia, renal failure, anemia, or lytic bone lesions) features felt related to the plasma cell disorder
- Bone marrow clonal plasmacytosis ≥60%
- Serum involved/uninvolved free light chain (FLC) ratio ≥100 (provided involved FLC is ≥100 mg/L)
1 focal lesion on magnetic resonance imaging
Comparison of Diagnostic Criteria
A retrospective study of 227 cases compared the efficacy of five diagnostic criteria for multiple myeloma, finding that:
- The Traditional Domestic criteria had the highest misdiagnosis rate due to high fixed bone marrow plasma cell percentage and serum M-protein thresholds 5
- The WHO criteria and the International Myeloma Working Group 2009 criteria exhibited relatively low misdiagnosis rates due to their lower bone marrow plasma cell percentage thresholds and detailed end-organ damage descriptions 5
- The 2003 International Myeloma Working Group criteria and the 2011 Chinese Myeloma Working Group criteria exhibited perfect performance, focusing on monoclonal plasma cell proliferation rather than fixed thresholds 5
Importance of Accurate Diagnosis
Accurate diagnosis of multiple myeloma is crucial, as distinguishing symptomatic multiple myeloma from precursor stages such as monoclonal gammopathy of undetermined significance and smouldering multiple myeloma is essential for determining treatment approaches 6