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 volumea

 
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 leukemiab

  • – 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) 
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 volumea

 
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 leukemiab

  • – 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) 
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