A 68-year-old man with multiple myeloma on lenalidomide-dexamethasone develops deep vein thrombosis. Serum M-protein is 1.8 g/dL; calcium 11.2 mg/dL; creatinine 1.6 mg/dL; hemoglobin 9.4 g/dL. His ISS stage (International Staging System) is determined by which TWO parameters?
- A Serum albumin and serum beta-2 microglobulin ✓
- B Serum calcium and creatinine
- C Hemoglobin and M-protein level
- D LDH and cytogenetics
Correct answer: A. Serum albumin and serum beta-2 microglobulin
Explanation
The original International Staging System (ISS) for multiple myeloma uses only two parameters: serum beta-2 microglobulin (B2M) and serum albumin. ISS Stage I: B2M <3.5 mg/L + albumin ≥3.5 g/dL. Stage II: neither Stage I nor III. Stage III: B2M ≥5.5 mg/L. The Revised ISS (R-ISS) adds LDH and cytogenetics (del17p, t(4;14), t(14;16)) but the original ISS relies solely on B2M and albumin. Calcium, creatinine, and hemoglobin are part of the CRAB criteria defining end-organ damage, not staging.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.