Diagnostic criteria for essential thrombocytosis
| Persistent thrombocytosis more than 400 000/μL in the absence of a reactive cause* |
| Absence of iron deficiency (normal serum ferritin for sex) |
| JAK2 V617F assay (peripheral blood; expression establishes the presence of an MPD but not its type; absence does not exclude an MPD) |
| Hemoglobin less than 16 g/dL in a man or less than 14 g/dL in a woman (hematocrit < 47% in a man or < 44% in a woman) in the absence of splenomegaly; otherwise, red cell mass and plasma volume determinations are mandatory if a JAK2 V617F assay is positive |
| Negative Bcr-Abl FISH (peripheral blood) if a JAK2 V617F assay is negative |
| If there is anemia, macrocytosis, or leukopenia, or evidence of extramedullary hematopoiesis (ie, circulating nucleated erythrocytes, immature myelocytes, or splenomegaly), a bone marrow examination (including flow cytometry and cytogenetics) is mandatory regardless of JAK2 V617F expression status |
| Persistent thrombocytosis more than 400 000/μL in the absence of a reactive cause* |
| Absence of iron deficiency (normal serum ferritin for sex) |
| JAK2 V617F assay (peripheral blood; expression establishes the presence of an MPD but not its type; absence does not exclude an MPD) |
| Hemoglobin less than 16 g/dL in a man or less than 14 g/dL in a woman (hematocrit < 47% in a man or < 44% in a woman) in the absence of splenomegaly; otherwise, red cell mass and plasma volume determinations are mandatory if a JAK2 V617F assay is positive |
| Negative Bcr-Abl FISH (peripheral blood) if a JAK2 V617F assay is negative |
| If there is anemia, macrocytosis, or leukopenia, or evidence of extramedullary hematopoiesis (ie, circulating nucleated erythrocytes, immature myelocytes, or splenomegaly), a bone marrow examination (including flow cytometry and cytogenetics) is mandatory regardless of JAK2 V617F expression status |
MPD indicates myeloproliferative disorder; and FISH, fluorescent in situ hybridization.
As indicated in the text, MPD patients represent only a minority of thrombocytosis patients in general but constitute most of those with persistent thrombocytosis in the absence of a definable cause.