Risk categoryAge < 60 yearsAge ≥ 60 yearsWomen of childbearing age
Low riskNo treatment* or low-dose aspirin‡Not applicableNo treatment† or low-dose aspirin‡
Intermediate riskNo treatment* or anagrelide‡ or low-dose aspirin‡Not applicableNo treatment† or low-dose aspirin‡
Platelet count <1,500 × 103 per μL (1,500 × 109 per L)
Intermediate riskNo treatment† or anagrelide‡Not applicableNo treatment†
Platelet count >1,500 × 103 per μL
High riskHydroxyurea§ or anagrelide* plus low-dose aspirin†Hydroxyurea§ plus low-dose aspirin†Interferon alfa|| plus low-dose aspirin†