Comparison of effect sizes between JAK2V617F-positive ET versus controls and JAK2V617F-positive PV versus controls revealed significantly larger effect for rs12339666 in PV (JAK2; Breslow–Day P =2.452 × 10−11) and rs9376092 in ET (HBS1L-MYB; Breslow–Day P=0.0004; Table 2B). This evidence concerns the gene JAK2 and essential thrombocythemia.