Table 2.

World Health Organization 2016 criteria for the diagnosis of polycythemia vera. A diagnosis of polycythemia vera requires either all three major criteria, or the first two major criteria plus the minor criterion

Major criteria
Criterion no. 1, clinical
Hemoglobin	> 16.5 g/dL in men, > 16.0 g/dL in women
Hematocrit	> 49% in men, > 48% in women
Red cell mass	25% increase above mean normal predicted value
Criterion no. 2, morphological
Bone marrow morphology*	Hypercellularity for age with trilineage growth (panmyelosis), including prominent erythroid, granulocytic, and megakaryocytic proliferation with pleomorphic, mature megakaryocytes (differences in size)
Criterion no. 3, genetic
JAK2 V617F mutation or JAK2 exon 12 mutation	Present
Minor criterion
Serum erythropoietin level	Subnormal

JAK2, Janus kinase 2; *, major criterion no. 2 may not be required in cases with sustained absolute erythrocytosis: hemoglobin levels >18.5 g/ dL in men (hematocrit, 55.5%) or > 16.5 g/dL in women (hematocrit, 49.5%) if major criterion no. 3 and the minor criterion are present. However, initial myelofibrosis (present in up to 20% of patients) can be detected only with a bone marrow biopsy; this finding may predict a more rapid progression to secondary myelofibrosis