Correlations between IL-1ra and JAK2V617F allele burden of PB and fibrocytes and the percentage of SLAMF7high CD16− monocytes in PB, MF onset, and splenomegaly. (A) The positive correlation between IL-1ra and the JAK2V617F allele burden of PB (n = 24) (r = 0.784; R2 = 0.615; P < .0001). Pearson’s correlation coefficient was calculated, and the statistical significance was calculated using linear regression analysis. (B) The positive correlation between IL-1ra and the JAK2V617F allele burden of fibrocytes (n = 24) (r = 0.661; R2 = 0.436; P = .0006). Pearson’s correlation coefficient was calculated, and the statistical significance was calculated using linear regression analysis. (C) The positive correlation between IL-1ra and the percentage of SLAMF7highCD16− monocytes in PB (n = 24) (r = 0.715; R2 = 0.512; P < .0001). Pearson’s correlation coefficient was calculated, and the statistical significance was determined using linear regression analysis. (D) Comparison of IL-1ra between MPN patients with MF who harbor JAK2V617F and those without MF. The results are reported as medians. MPN patients with MF who harbor JAK2V617F (n = 17) had significantly higher IL-1ra than those without MF (n = 7) (median: 1550.8 pg/mL vs 411.3 pg/mL, Mann-Whitney U test P < .007). The results are reported as medians. (E) ROC curve showing the cutoff value of IL-1ra for separating MPN patients with MF who harbor a JAK2V617F mutation from those without MF. The AUC was 0.857, and the sensitivity and specificity for classifying MF onset were 82.4% and 85.7%, respectively, with the cutoff value of IL-1ra set to >600 pg/mL. (F) Comparison of IL-1ra between MPN patients with splenomegaly who harbor JAK2V617F and those without splenomegaly. The results are reported as medians. MPN patients with splenomegaly who harbor JAK2V617F (n = 10) also had a significantly higher IL-1ra than those without splenomegaly (n = 14) (median: 1570.1 pg/mL vs 476.1 pg/mL, Mann-Whitney U test P < .007). (G) ROC curve showing the cutoff value of IL-1ra for separating MPN patients with splenomegaly who harbor a JAK2V617F mutation from those without splenomegaly. The AUC was 0.829, and the sensitivity and specificity for classifying MF onset were 90.0% and 78.6%, respectively, with the cutoff of IL-1ra set to >800 pg/mL. The results are reported as medians. Statistical significance was assessed using Mann-Whitney U test. **P < .01.