ET patients with mutant CALR had lower WBC counts (7.5±4.1×109/L; p<0.001), lower hemoglobin levels (137±34.2 g/L; p=0.002), and higher platelet counts (982±24.2×109/L; p<0.001) than those with mutant JAK2V617F (14±11.0×109/L, 145±21.4 g/L, 515±31.6×109/L). Here, CALR is linked to essential thrombocythemia.