Validation of ALL-HT in 2 independent B-ALL cohorts. (A-B) ROC curve for performance of ALL-HT score and outcome of severe prolonged neutropenia in 2 separate external validation cohorts. AUC, P value, and number of patients (n) are provided. (C-D) ALL-HT risk group assignment and the outcome of severe prolonged neutropenia in 2 validation cohorts. Fischer exact test performed to compare differences between groups. (E-F) Cumulative days of grade 4 neutropenia (ANC <500/μL) between D0 and D30 by ALL-HT risk group. Median with 95% confidence intervals are included. Mann Whitney U test was performed to compare cumulative days of neutropenia between LR and HR groups, ∗∗∗∗P < .0001. (G-H) Kaplan-Meier curve for OS by ALL-HT risk group in 2 external cohorts, where the event was death and patients who had not experienced this event were censored at time of last follow up. Log-rank P value, median OS (mOS), and number of patients in each group are included.