Multiple Myeloma Diagnostic Criteria (https://www.myeloma.org/newly-diagnosed/multiple-myeloma-diagnostic-criteria)
Multiple Myeloma Diagnostic Criteria
The CRAB Criteria
The IMF International Myeloma Working Group (IMWG), the research arm of the IMF, is one of the most prestigious organizations for myeloma experts. IMWG members conduct collaborative basic, clinical, and translational research to improve outcomes for patients while providing scientifically validated, critically appraised consensus guidelines for healthcare providers, including criteria on myeloma diagnosis, treatment, supportive care, testing, and more. In 2003, the IMWG first published the CRAB criteria.
Any ONE of the CRAB criteria can indicate the presence of end-organ damage due to myeloma:
- Calcium – elevated level in the serum (blood) more than 11mg/dL (higher than the upper limit of normal).
- Renal (kidney) impairment – creatinine clearance <40 mL per minute or serum creatinine >2 mg/dL.
- Anemia (low red blood cell count) – hemoglobin value <10 g/dL.
- Bone damage (at least one osteolytic lesion) – if bone marrow has <10% clonal plasma cells, more than one bone lesion is required to distinguish myeloma from a solitary plasmacytoma.
The SLiM CRAB Criteria
In 2014, the IMWG expanded the CRAB criteria by adding 3 new SLiM biomarkers that indicate active myeloma before end-organ damage occurs.
- Sixty percent (60%) monoclonal plasma cells present in the bone marrow.
- Light chains ratio of involved-to-uninvolved sFLC of 100 or more.
- Involved FLC level must be ≥100 mg/L.
- Uninvolved light chains are those that are not made by myeloma cells.
- MRI imaging of 2 or more focal lesions in bone marrow.
In brief, the current IMWG guidelines state that the diagnosis of active myeloma must include BOTH of the following:
- Presence of monoclonal plasma cells in the bone marrow ≥10% or biopsy-proven bony or extramedullary plasmacytoma (a tumor of monoclonal plasma cells that is found in soft tissue outside of the bone marrow and separate from bone).
- Evidence of at least one SLiMCRAB myeloma-defining event (MDE).
Understand the CRAB Criteria for Myeloma Diagnosis
Health professionals rely on the CRAB criteria to diagnose multiple myeloma. CRAB is an acronym that stands for:
C: Calcium elevation
R: Renal problems (kidney dysfunction)
A: Anemia
B: Bone lesions
| Effects of Increased Myeloma Cells in the Bone Marrow CRAB criteria | Cause | Impact on Patient |
| C - Calcium levels in the blood are increased | Release of calcium from damaged bone into bloodstream. |
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| R -Renal problems — kidney damage (https://www.myeloma.org/what-is-kidney-failure) | M-proteins can pass from the bloodstream into the urine, causing kidney damage. High blood calcium, infections, and other factors can also cause or increase kidney damage. |
|
| A - Anemia (https://www.myeloma.org/multiple-myeloma-anemia) | Decrease in the number and activity of red blood cell-producing cells in the bone marrow. |
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B - Bone damage Osteoporosis (thinning) or more severe damage (e.g. lytic lesions, fractures, collapse of a vertebra) (Learn more at Bone Disease (https://www.myeloma.org/bone-disease).) | Myeloma cells activate osteoclast cells (which destroy bone) and block osteoblast cells (which repair bone). |
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| Other types of organ dysfunction | Local or systemic effects of myeloma, other than CRAB features. |
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| Abnormal immune function | The myeloma cells reduce the number and activity of normal plasma cells capable of producing antibodies against infection. |
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What's Next?
What Are Monoclonal Gammopathy of Undetermined Significance, Smoldering Multiple Myeloma, and Active Myeloma? (https://www.myeloma.org/what-are-mgus-smm-mm)
Before developing active myeloma, patients pass through the earlier stages: monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM). Learn about the stages of the disease.