JAK2 and acquired polycythemia vera: Lastly, JAK2 V617F mutant allele burden was found much higher in polycythemia vera (PV) patients [median(P25–P75): 45.02%(35.12%–54.22%)] than in essential thrombocythemia (ET) patients [median(P25–P75): 28.23%(17.77%–41.66%)], and that it increased with WBC counts (r = 0.393, p = 0.000) and RBC counts(r = 0.215, p = 0.001), other than platelet counts (r = −0.051, p = 0.452).