TABLE 1.

Summary of diagnostic criteria for MGUS, SM and MM

	Monoclonal protein and clonal bone marrow plasma cells	Myeloma defining event (biomarker of malignancy a or end‐organ damage)
MGUS	Serum monoclonal protein <30 g/L and urinary monoclonal protein <500 mg per 24 hours and clonal bone marrow plasma cells <10%	No
SM	Serum monoclonal protein ≥30 g/L or urinary monoclonal protein ≥500 mg per 24 hours or clonal bone marrow plasma cells 10% to 60%	No
MM	Clonal bone marrow plasma cells ≥10% or biopsy‐proven plasmacytoma	Yes

Abbreviations: MGUS, monoclonal gammopathy of undetermined significance; SM smoldering myeloma; MM, multiple myeloma. FLC ratio, involved versus uninvolved serum‐free light chain ratio.

^a Biomarker of malignancy: ≥60% clonal bone marrow plasma cells; ≥100 FLC ratio (absolute level of the involved light chain is at least 100 mg/L); >1 lesion by magnetic resonance imaging (≥5 mm in size). End‐organ damage (due to myeloma): hypercalcemia (serum calcium >0.25 mmol/L [>1 mg/dL] higher than the upper limit of normal or >2.75 mmol/L [>11 mg/dL]); renal insufficiency (creatinine clearance <40 mL per minute or serum creatinine >177 mol/L [>2 mg/dL]); anemia (hemoglobin >20 g/L below the lowest limit of normal or hemoglobin <100 g/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.