LCN2 levels are elevated in MPN plasma. (A) An enzyme-linked immunosorbent assay was used to quantitate LCN2 levels in plasma isolated from normal donors (n = 16) and patients with PV (n = 30), ET (n = 30), PMF (n = 30), PV-MF (n = 20), or ET-MF (n = 20) (Kruskal-Wallis nonparametric ANOVA; P < .0001 comparing normal plasma vs plasma from each type of MPN; P = .018 comparing PMF vs PV or ET). Plasma LCN2 levels in PV-MF and ET-MF were greater than those present in PV and ET plasmas, respectively (Wilcoxon rank sum tests; P = .0002 and P = .018, respectively).The numbers indicate the median LCN2 level present in the plasma of patients with a particular MPN. The nonparametric Spearman correlation coefficient analysis showed an inverse relationship between hemoglobin levels and LCN2 levels (coefficient, −0.35; P < .0001; n = 117) (B) and an inverse correlation between platelet counts and LCN2 levels (coefficient= −0.26, P = .0044, n = 117) (C). (D) The plasma LCN2 levels were not significantly different in those patients who had more severe degrees of MF as assessed by the number of prognostic variables that characterized their MF (Kruskal-Wallis nonparametric ANOVA; P > .05 at number 0 vs each of the others). ANOVA, analysis of variance.