Stage	Criteria	Cell mass
I	All of the following: haemoglobin value > 10 g/dL normal serum calcium value of < 12 mg/dL normal bone structure or one solitary bone lesion only on radiography low M‐component production rates IgG < 5 g/dL IgA < 3 g/dL urine light chain M‐component on electrophoresis of < 4 g/24 h	< 0.6 x 1012 cells/mm2
II	One or more of the following: haemoglobin value of ≤ 10g/dL and ≥ 8.5g/dL normal serum calcium value of ≤ 12mg/dL normal bone structure or one solitary bone lesion only on radiography M‐component production rates IgG ≥ 5 g/dL and ≤ 7 g/dL IgA ≥ 3 g/dL and ≤ 5 g/dL urine light chain M‐component on electrophoresis of ≥ 4 g/24 h and ≤ 12 g/24h	≥ 0.6 x 1012 cells/mm2 and ≤ 1.2 x 1012 cells/mm2
III	One or more of the following: haemoglobin value of < 8.5 g/dL serum calcium value of > 12 mg/dL advanced lytic bone lesions high M‐component production rates IgG > 7 g/dL IgA > 5 g/dL urine light chain M‐component on electrophoresis of > 12 g/24 h	> 1.2 x 1012 cells/mm2