Essential Thrombocytosis - Diagnostic Criteria

Diagnostic Criteria

The diagnosis of essential thrombocythemia requires the presence of a persistent thrombocytosis of greater than 600 × 103/µL in the absence of an alternative cause.

The following revised diagnostic criteria for essential thrombocythemia were proposed in 2005. The diagnosis requires the presence of both A criteria together with B3 to B6, or of criterion A1 together with B1 to B6.

• A1. Platelet count > 600 × 103/µL for at least 2 months
• A2. Acquired V617F JAK2 mutation present
• B1. No cause for a reactive thrombocytosis
  • normal inflammatory indices
• B2. No evidence of iron deficiency
  • stainable iron in the bone marrow or normal red cell mean corpuscular volume
• B3. No evidence of polycythemia vera
  • hematocrit < midpoint of normal range or normal red cell mass in presence of normal iron stores
• B4. No evidence of chronic myeloid leukemia
  • But the Philadelphia chromosome may be present in up to 10% of cases. Patients with the Philadelphia chromosome have a potential for the development of acute leukemia, especially acute lymphocytic leukemia.
• 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