This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Misc. (W.B.C), Subject name: Pathology
The single most important predictor of survival in multiple myeloma 
Select and explain. 
A. IL-6 levels, B. Bence jones proteinuria, C. CD 138 positivity, D. Serum b2-microglobulin
D: Serum b2-microglobulin
Answer: D: Serum b2-microglobulin 
Explanation: Ans. (d) Serum b2 -microglobulin(Ref: Robbins 9th/pg 598-602/8th 608-612)b2-M concentration is the strongest and most reliable prognostic factor for multiple myeloma. It depends not only on tumor burden but also on renal function. Elevated b2-M values predict early death