TABLE 1

Diagnostic criteria for MGUS, smoldering multiple myeloma, and active multiple myeloma

Monoclonal gammopathy of undetermined significance (MGUS)
Serum monoclonal (M) protein < 3 g/dL
Clonal bone marrow plasma cells < 10%a
Absence of myeloma-defining events or light-chain amyloidosis
Smoldering multiple myeloma
Serum M protein ≥ 3 g/dL or clonal bone marrow plasma cells 10%–60%, or both
Absence of myeloma-defining events or light-chain amyloidosis
Symptomatic multiple myeloma
Clonal bone marrow plasma cells ≥ 10% or plasmacytoma and ≥ 1 myeloma-defining event:

  • Calcium: hypercalcemia, ie, serum calcium > 1 mg/dL higher than the upper limit of normal or > 11 mg/dL

  • Renal insufficiency: creatinine clearance < 40 mL/minute or serum creatinine > 2 mg/dL

  • Anemia: hemoglobin > 2 g/dL below the lower limit of normal, or < 10 g/dL

  • Bone involvement: ≥ 1 lytic lesions on skeletal radiography, computed tomography, or positron emission tomography– computed tomography

Clonal bone marrow plasma cell percentage ≥ 60%
Involved: uninvolved serum free light chain ratio ≥ 100 with involved free light chain ≥ 100 mg/L
More than 1 focal lesion on magnetic resonance imaging b

  • ↵a Can be omitted in patients with low-risk MGUS.

  • ↵b As opposed to diffuse lesions (diffuse marrow infiltration). Magnetic resonance imaging of the whole body–or at least of the spine and pelvis if whole-body imaging is not feasible–is preferred. Lesions should be > 5 mm in size.

  • Based on information in reference 7.