Criteria for the diagnosis of ET
| WHO 2008 . | BCSH 2010 . |
|---|---|
| Requires A1-A4 | Requires A1-A3 or A1 + A3-A5 |
| A1: Sustained platelet count >450 × 109/L | A1: Sustained platelet count >450 × 109/L |
| A2: Bone marrow showing increased numbers of enlarged, mature megakaryocytes; no significant increase of left-shift of granulopoiesis or erythropoiesis* | A2: Presence of an acquired pathogenetic mutation (eg, in JAK2 or MPL) |
| A3: Not meeting WHO criteria for PV, PMF, CML, MDS, or other myeloid neoplasm | A3: No other myeloid malignancy, especially PV, PMF, CML, or MDS |
| A4: Acquired mutation or clonal marker or no reactive cause for thrombocytosis | A4: No reactive cause for thrombocytosis and normal iron stores |
| A5: Bone marrow aspirate and trephine biopsy showing increased megakaryocyte numbers displaying a spectrum of morphology with predominant large megakaryocytes with hyperlobated nuclei and abundant cytoplasm. |
| WHO 2008 . | BCSH 2010 . |
|---|---|
| Requires A1-A4 | Requires A1-A3 or A1 + A3-A5 |
| A1: Sustained platelet count >450 × 109/L | A1: Sustained platelet count >450 × 109/L |
| A2: Bone marrow showing increased numbers of enlarged, mature megakaryocytes; no significant increase of left-shift of granulopoiesis or erythropoiesis* | A2: Presence of an acquired pathogenetic mutation (eg, in JAK2 or MPL) |
| A3: Not meeting WHO criteria for PV, PMF, CML, MDS, or other myeloid neoplasm | A3: No other myeloid malignancy, especially PV, PMF, CML, or MDS |
| A4: Acquired mutation or clonal marker or no reactive cause for thrombocytosis | A4: No reactive cause for thrombocytosis and normal iron stores |
| A5: Bone marrow aspirate and trephine biopsy showing increased megakaryocyte numbers displaying a spectrum of morphology with predominant large megakaryocytes with hyperlobated nuclei and abundant cytoplasm. |
BCSH indicates British Committee for Standards in Haematology; CML, chronic myeloid leukemia; ET, essential thrombocythemia; MDS, myelodysplastic syndromes; MPN, myeloproliferative neoplasm; PMF, primary myelofibrosis; PV, polycythemia vera; and WHO, World Health Organization.
Increased reticulin fibrosis excludes a diagnosis of ET