Essential Thrombocythemia Diagnosis

Diagnostic criteria for essential thrombocythemia (ET), World Health Organisation 2008

All four of the following diagnostic criteria must be met:

  1. Thrombocytosis ≥ 450 x109/L, sustained during work-up
  2. Increased numbers of enlarged, mature megakaryocytes on bone marrow biopsy, with no significant increase or left-shift of granulopoiesis or erythropoiesis
  3. Patient does NOT meet WHO criteria for:
  4. Presence of JAK2 V617F or other clonal marker, OR in the absence of JAK2 V617F, no evidence for a reactive thrombocytosis (e)

(a) if serum ferritin reduced, WHO guidelines state exclusion of polycythemia requires failure of iron replacement to raise the hemoglobin to the polycythemia vera range (PV exclusion based on hemoglobin and hematocrit levels – red cell mass measurement not required)
(b) requires absence of relevant reticulin fibrosis, collagen fibrosis, leukoerythroblastosis or marrow morphology typical for primary myelofibrosis (small to large megakaryocytes, aberrant N:C ratio, hyperchromatic, bulbous or irregularly folded nuclei, dense clustering)
(c) BCR-ABL1 must be absent
(d) dyserythropoiesis and dysgranulopoiesis must be absent
(e) Causes of reactive thrombocytosis include: iron deficiency, splenectomy, surgery, infection, inflammation, connective tissue disorder, metastatic malignancy, lymphoproliferative disorder