Risk category		Age < 60 years	Age ≥ 60 years	Women of childbearing age
Low risk		No treatment* or low-dose aspirin‡	Not applicable	No treatment† or low-dose aspirin‡
Intermediate risk		No treatment* or anagrelide‡ or low-dose aspirin‡	Not applicable	No treatment† or low-dose aspirin‡
	Platelet count <1,500 × 103 per μL (1,500 × 109 per L)
Intermediate risk		No treatment† or anagrelide‡	Not applicable	No treatment†
	Platelet count >1,500 × 103 per μL
High risk		Hydroxyurea§ or anagrelide* plus low-dose aspirin†	Hydroxyurea§ plus low-dose aspirin†	Interferon alfa|| plus low-dose aspirin†