Yes, I had my JAK2 done in June 2007. It confirms the diagnoses whether ET is there or CML. CML & ET are very similar in nature but treatment is altogether is different. You can get this test done from any lab. They will take your blood.
If it is negative than it will be confirmed ET.
I think if you are on Hydrea since last 5 years than you are confirmed ET, but get your JAK2 Mutation Gene Test done.
To avoid weakness of Hydrea, take as much water as you can so that you can excrete more & more.
I'm 27 years old & took around 3 years as I was diagnosed in December 1994.
If you are living in USA, you can also contact Mayo Clinic as they have more details about ET.
Take care & don't worry. ET just distrubs the quality of life, it doesn't reduce the age of a person.
Best regards,
Zeeshan