Diagnosing Essential Thrombocythemia

Diagnostic Criteria

Diagnostic criteria for the MPNs, including ET, polycythemia vera, and primary myelofibrosis, were updated in 2016 by the World Health Organization (WHO).1

Essential thrombocythemia (ET)
Major criteria:
  • Platelet count ≥450 × 109/L
  • Bone marrow biopsy showing proliferation mainly of the megakaryocyte lineage with increased numbers of enlarged, mature megakaryocytes with hyperlobulated nuclei; no significant increase or left shift in neutrophil granulopoiesis or erythropoiesis and very rarely minor (grade 1) increase in reticulin fibers
  • Not meeting WHO criteria for BCR-ABL1+ CML, PV, PMF, myelodysplastic syndromes, or other myeloid neoplasms
  • Presence of JAK2, CALR, or MPL mutation
Minor criterion:
  • Presence of clonal marker or absence of evidence for reactive thrombocytosis
BM = bone marrow CALR = calreticulin CML = chronic myelogenous leukemia Hb = hemoglobin Hct = hematocrit JAK = Janus-associated kinase MPL = myeloproliferative leukemia virus oncogene
Adapted from Arber DA et al. Blood. 2016;127(20):2391-2405.

1. Arber DA, Orazi A, Hasserjian R, et al. Blood. 2016;127(20):2391-2405.