| Stage | Criteria |
| I | Serum beta‐2 microglobulin < 3.5 mg/L plus serum albumin ≥ 3.5 g/dL |
| II | Not stage I or IIIa |
| III | Serum beta‐2 microglobulin ≥ 5.5 mg/L |
| Stage | Criteria |
| I | Serum beta‐2 microglobulin < 3.5 mg/L plus serum albumin ≥ 3.5 g/dL |
| II | Not stage I or IIIa |
| III | Serum beta‐2 microglobulin ≥ 5.5 mg/L |