I done think there’s anything different between ET & PV per se. I have recently ( 4 months ago) been diagnosed with PV and the way the MPN specialist did this was by keeping an eye on my Haematocrit levels. This is the marker that shows if your red bloods cells are ok! My levels were .49 and they like them to be below .45. This level can contribute to strokes and heart attacks being more prevalent. The way I have been managed to date is to have 4 venesections to date- ( so by removing a pint of blood) much as if you were giving a blood donation. This has after 4 months brought my levels to under .45. So my specialist is happy. I have however gone from 8 weekly bloods to 6 weekly bloods. I am still on my Peg Interferon weekly and asprin . I don’t take Hydroxyeurea as after 24 years on what was a wonder drug for me - stopped working. Hope this explains and helps!