LAP expression on circulating granulocytes from control subjects without JAK2 (V617F) mutant alleles and from patients with PV or post-PV MF carrying the mutation. Control subjects include healthy individuals and patients with secondary erythrocytosis who did not carry the JAK2 (V617F) mutation. Twenty-one patients with PV or post-PV MF are subdivided into 2 groups according to the percentage of JAK2 (V617F) mutant alleles in their granulocytes (≤ 50% versus > 50%). LAP expression levels are shown in a box plot. The Kruskal-Wallis test showed significant differences between these groups (P < .001).