All patients:

• – manage reversible cardiovascular risk factors aggressively (e.g., smoking, hypertension, hypercholesterolemia, obesity)

High-risk patients (prior thrombosis or age > 60 years or platelets > 1500 x 10⁹/L):

• – low-dose aspirin plus hydroxyurea (anagrelide or interferon-α second line)

Intermediate-risk patients (age 40–60 years, no high-risk features):

• – either enter into randomized trial (e.g., PT-1 intermediate risk arm)

• – or low-dose aspirin (consider cytoreduction if other cardiovascular risk factors present)

Low-risk patients (age < 40 years and no high-risk features):

• – low-dose aspirin