International Myeloma Working Group (IMWG) criteria for the diagnosis of multiple myeloma

Making the Diagnosis of Multiple Myeloma 

Unlike many cancers, the diagnosis of active myeloma that requires therapy is based upon a combination of factors. A bone marrow biopsy (or biopsy from a tissue site where myeloma may have spread) is an essential part of the diagnosis. If the percentage of plasma cells is high, e.g. > 60%, the diagnosis of active myeloma is highly likely and part of the new revised criteria. However, with lesser myeloma percentage numbers, other factors must support the diagnosis. 

For decades the diagnosis of multiple myeloma required the presence of end-organ damage known as the CRAB criteria, including increased calcium level, renal dysfunction, anemia, and destructive bone lesions. The updated criteria allow for treatment of patients who are at such high risk of progression to symptomatic disease so that it is clear these patients would benefit from therapy and potentially live longer if they were treated before serious organ damage occurred. 

The updated criteria for the diagnosis of myeloma represent a paradigm shift in the approach to myeloma and have considerable impact on the management of the disease. 

The revised IMWG criteria allow, in addition to the classic CRAB features, three myeloma defining events (MDEs). The presence of at least one of these markers is considered sufficient for a diagnosis of multiple myeloma, regardless of the presence or absence of symptoms or CRAB features. Each of these markers has been shown in two or more independent studies to be associated with an approximately 80% or higher risk of developing myeloma-related organ damage within two years. 

The new definition of active multiple myeloma is:

Clonal bone marrow plasma cells >10% or biopsy-proven bony or extramedullary plasmacytoma and any one or more of the following CRAB features and myeloma-defining events:

Original CRAB Criteria for the Diagnosis of Multiple Myeloma 

• Evidence of end organ damage that can be attributed to the underlying plasma cell proliferative disorder, specifically:
  • Hypercalcemia: serum calcium >0.25 mmol/L (>1mg/dL) higher than the upper limit of normal or >2.75 mmol/L (>11mg/dL)
  • Renal insufficiency: creatinine clearance <40 mL per minute or serum creatinine >177mol/L (>2mg/dL)
  • Anemia: hemoglobin value of >20g/L below the lowest limit of normal, or a hemoglobin value <100g/L
  • Bone lesions: one or more osteolytic lesion on skeletal radiography, CT, or PET/CT. If bone marrow has <10% clonal plasma cells, more than one bone lesion is required to distinguish from solitary plasmacytoma with minimal marrow involvement

New Diagnostic Criteria

• Any one or more of the following biomarkers of malignancy, or myeloma-defining events (MDEs):
  • 60% or greater clonal plasma cells on bone marrow examination
  • Serum involved / uninvolved free light chain ratio of 100 or greater, provided the absolute level of the involved light chain is at least 100mg/L (a patient's involved free light chain either kappa or lambda is the one that is above the normal reference range; the uninvolved free light chain is the one that is typically in, or below, the normal range)
  • More than one focal lesion on MRI that is at least 5mm or greater in size.

  Patients who are diagnosed with myeloma based upon laboratory tests but do not have any active symptoms must discuss all results carefully with their treating physician. It may be that treatment should be started immediately. Or, if results are borderline or not clear, it may be that treatment can be deferred--pending follow-up or additional testing.

  At this time, it is often helpful to consult with a myeloma expert and get a second opinion to be sure of the best strategies.

  With the introduction of the New Diagnostic Criteria, the definitions for earlier or pre-myeloma disease states also change. For example, smoldering multiple myeloma (SMM) can have a bone marrow percentage from 10% to less than 60 %. Less than 10% is considered MGUS, and greater than 60% is considered active myeloma by the new criteria.

Recommended exam, tests, and imaging studies for the diagnosis of myeloma

1. History and Physical Examination See Palumbo, A. et. al Revised International Staging System for Multiple Myeloma: A Report From International Myeloma Working Group.

2. Routine Laboratory Testing

• Tests to assess blood cells, including a Complete Blood Count
• Tests to assess kidney function, including serum creatinine, creatinine clearance, estimated glomerular filtration gate (eGFR), electrolyte levels, and blood urea nitrogen (BUN)
• Tests to assess proteins and other substances in the blood, including calcium levels, total protein test, serum beta-2 microglobulin (sβ2M), lactate dehydrogenase (LDH), C-reactive protein, and blood sugar or blood glucose test
• Tests to assess monoclonal protein, including serum protein electrophoresis (SPEP), immunofixation electrophoresis of blood or urine (IFE), quantitative immunoglobulins testing (QIg), serum free light chain assay (brand name Freelite®), and serum heavy/light chain assay, or (brand name Hevylite® Test)

3. Bone Marrow Testing: Obtain an aspirate plus trephine biopsy with testing for cytogenetics, fluorescent in situ hybridization (FISH), and immunophenotyping.

4. Testing for the Bones

• Bone survey including spine, pelvis, skull, humeri and femurs.
• The IMWG now recommends the use of low-dose whole-body CT (LDWBCT) or MRI in the work-up of smoldering multiple myeloma (SMM) and solitary plasmacytoma.
• The IMWG now recommends that one of PET-CT, LDWBCT, or MRI of the whole body or spine be done in all patients with suspected smoldering myeloma, with the exact imaging modality determined by availability and resources.
• Clear evidence of one or more sites of osteolytic bone destruction (≥5mm in size) seen on CT (including LDWBCT) or PET-CT does fulfill the criteria for bone disease in multiple myeloma, and should be regarded as meeting the CRAB requirement irrespective of whether the lesions can be visualized on skeletal radiography or not.
• Increased uptake on PET-CT alone is not adequate for the diagnosis of multiple myeloma; evidence of underlying osteolytic bone destruction is needed on the CT portion of the examination.
• Bone densitometry studies are not sufficient to determine presence of multiple myeloma.
• The IMWG no longer recommends the presence of osteoporosis or vertebral compression fractures in the absence of lytic lesions as being sufficient evidence of bone disease for purposes of the diagnostic criteria.

4. Imaging

• Complete blood count with differential and peripheral blood smear review
• Chemistry panel including calcium and creatinine
• Serum protein electrophoresis, immunofixation
• Nephelometric quantitation of immunoglobulins
• Routine urinalysis, 24h urine collection for proteinuria,electrophoresis and immunofixation
• Quantification of both urine M-component level and albuminuria

Detailed review of all these results may require input from a myeloma expert physician. 

The table below lists the criteria for a range of plasma cell disorders separate from active myeloma.

Learn More at

Lancet Oncol. 2014 Nov;15(12):e538-48. doi: 10.1016/S1470-2045(14)70442-5. Epub 2014 Oct 26.