Unifying Concepts

Diagnostic Criteria for Essential Thrombocytopaenia (ET)

Polycythemia Vera Study Group (PVSG) Diagnostic Criteria for Essential Thrombocytopaenia (ET)

All of the following criteria must be fulfilled to make a diagnosis of ET

  1. Platelet count greater than 600 x 109/L

  2. Hematocrit less than 40 or normal red blood cell mass

  3. Stainable iron in the marrow or normal RBC mean corpuscular volume (If these measurements suggest iron deficiency, polycythemia vera cannot be excluded unless a trial of iron therapy fails to increase the red blood cell mass into the polycythemic range.)

  4. No Philadelphia chromosome or bcr/abl gene rearrangement

  5. Collagen fibrosis of the bone marrow absent or less than one third of the biopsy area without both marked splenomegaly and a leukoerythroblastic blood film

  6. No cytogenetic or morphologic evidence for a myelodysplastic syndrome

  7. No cause for a reactive thrombocytosis

WHO Diagnostic Criteria for Essential Thrombocytopaenia (ET)

Positive criteria

  1. Sustained platelet count > 600x 109/l
  2. Bone marrow biopsy specimen showing proliferation mainly of the megakaryocytic lineage with increased numbers of enlarged, mature megakaryocytes

Criteria of exclusion

  1. No evidence of polycythaemia vera (PV)
    • Normal red cell mass or Hb <18.5 g/dl in men, 16.5g/dl in women
    • Stainable iron in marrow, normal serum ferritin or normal mean corpuscular volume (MCV)
    • If the former is not met, failure of iron trial to increase red cell mass or hemoglobin levels to the PV range
  2. No evidence of CML
    • No evidence of Philadelphia chromosome and no BCR/ABL fusion gene
  3. No evidence of idiopathic myelofibrosis
    • Collagen fibrosis absent
    • Reticulin fibrosis minimal or absent
  4. No evidence of myelodysplastic syndrome
    • No del(5q), t(3;3)(q21;26), inv(3)(q21q26)
    • No significant granulocytic dysplasia; few, if any, micromegakaryocytes
  5. No evidence that thrombocytosis is reactive due to:
    • Underlying inflammation or infection
    • Underlying neoplasm
    • Prior splenectomy


  1. Imbert M, Pierre R, Thiele J, Vardiman JW, Brunning RD, Flandrin G. Essential thrombocythaemia. In: Jaffe ES, Harris NL, Stein H, et al, editors. WHO classification of tumours: tumours of haematopoietic and lymphoid tissues. Lyon: IARC Press; 2001. p. 39-41.
  2. Murphy S, Peterson P, Iland H, Laszlo J. Experience of the Polycythemia Vera Study Group with essential thrombocythemia: a final report on diagnostic criteria, survival, and leukemic transition by treatment. Semin Hematol. 1997 Jan;34(1):29-39. [Medline]
  3. Harrison CN, Green AR. Essential thrombocythemia. Hematol Oncol Clin North Am. 2003 Oct;17(5):1175-90, vii. [Medline]


Created: Sep 03, 2007

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