I would suggest going to webside Leukemia/Lymphoma Society (renamed Blood Cancer United)
They have some wonderful booklets that have information on MPNs (ET is sub-category) they also
have lots of good booklets about medical tests for MPNs
btw MPN is the umbrella for about 4-5 sub-cats) MPN stands for MyeloProliferative Neoplasm......also if you register with Society, they will send you info about virtual lectures and in person conferences all over the USA. I've gone to the conference in NYC in ?March? and they have wonderful/knowledgeable speakers. MPN is rather rare so not all doctors or oncologists know all the details...