BM serum OPN expression by ELISA. Kaplan-Meier curves for OS (A) and EFS (B) of AML patients stratified for BM serum OPN expression. OS of patients with low (< 6.632 ng/mL) levels of OPN in the BM was significantly higher than in patients with high (≥ 6.632 ng/mL) OPN expression (P = .018; A). Similar differences were found for EFS (P = .008; B).