Hi I had a look at the NEJM pape Maz posted , and here is a direct link to the MPN Personalised Risk Calculator. It is, at the moment, the best there is. The more data you have about your MPN, the more accurate the risk assessment is.
cancer.sanger.ac.uk/mpn-mul...
I’ve also just found a link to the excellent 2018 NCCN patient guidelines to diagnosis and treatment of MPNs .
nccn.org/patients/guideline...
Very clear, evidence based and it has all the current info in one place. Lots of good diagrams and pictures, too, explaining what MPNs are
All the best,
Rachel