Criteria:
(1) sustained platelet count >= 450,000 per µL (elevated)
(2) proliferation of large, mature megakaryocytes in a bone marrow biopsy without a significant increase in cells from the granulocytic or erythyroid series
(3) one or both of the following:
(3a) presence of JAK2 mutation (JAK2 617V>F, other)
(3b) exclusion of reactive thrombocytosis
(4) exclusion of other myeloproliferative, myelodysplastic or bone marrow disorders
where:
• Causes of reactive thrombocytosis include inflammation, chronic infection, iron deficiency, surgery, metastatic cancer, autoimmune disorder, lymphoproliferative disorder, and post-splenectomy.
The diagnosis of ET requires the presence of all 4 criteria.
