Table 3. Proposed diagnostic criteria... | American Society of Hematology

Table 3.

Proposed diagnostic criteria for essential thrombocythemia (ET).

^a If these measurements suggest iron deficiency, PV cannot be excluded unless a trial of iron therapy fails to increase the red cell mass into the polycythemic range (patients need to be monitored closely since a rapid rise in hematocrit can precipitate thrombosis).
^b Rare patients have chronic myeloid leukemia coexisting with ET or other myeloproliferative diseases.³⁹
^c Approximately 5% of patients with myelodysplastic syndrome carry the V617F JAK2 mutation.
A1.	Platelet count > 600 x 10⁹/L for at least 2 months
A2.	Acquired JAK2 mutation
B1.	No cause for a reactive thrombocytosis – e.g., normal inflammatory indices
B2.	No evidence of iron deficiency – stainable iron in the marrow or normal red cell mean corpuscular volume^a
B3.	No evidence of PV – hematocrit < midpoint of normal range or normal red cell mass in presence of normal iron stores
B4.	No evidence of chronic myeloid leukemia^b – no Philadelphia chromosome or bcr-abl gene rearrangement
B5.	No evidence of myelofibrosis – no collagen fibrosis and ≤ grade 2 reticulin fibrosis (using 0–4 scale)
B6.	No evidence of a myelodysplastic syndrome – no significant dysplasia – no cytogenetic abnormalities suggestive of myelodysplasia
Diagnosis of ET requires A1+A2+B3–6 (V617F-positive ET) or A1+B1–6 (V617F-negative ET)