At 6 months, there were no significant differences in spleen responses (CALR: 21.4% versus JAK2: 25.7%, p = 0.33), but symptoms response was significantly lower in CALR-mutated patients (56.1% versus 66.7%, p = 0.04) and overall anemia was higher (60.3% versus 50.3%, p = 0.04). Here, JAK2 is linked to anemia.