Table 1.

Diagnostic criteria for polycythemia vera according to the World Health Organization (WHO) classification.

	2008 WHO Classification	2016 WHO Classification
Major Criteria	1. Hb > 18.5 g/dL in men/Hb > 16.5 g/dL in women or other evidence of increased RCM; 2. Presence of JAK2V617F or other functionally similar mutation such as JAK2 exon 12 mutation	1. Hb > 16.5 g/dL in men/Hb > 16.0 g/dL in women, or Hct > 49% in men/Hct > 48% in women, or increased RCM; 2. BM biopsy showing hypercellularity for age with trilineage growth (panmyelosis) including prominent erythroid, granulocytic, and megakaryocytic proliferation with pleomorphic, mature, megakaryocytes (differences in size); 3. Presence of JAK2V617F or JAK2 exon 12 mutation
Minor Criteria	1. BM biopsy showing hypercellularity for age with trilineage growth (panmyelosis) with prominent erythroid, granulocytic, and megakaryocytic proliferation; 2. Subnormal serum EPO level; 3. Endogenous erythroid colony formation in vitro	Subnormal serum EPO level
Criteria required for diagnosis	All 2 major and 1 minor or the first major and 2 minor criteria	All 3 major or the first 2 major and the minor criterion

Abbreviations: Hb: hemoglobin; Hct, hematocrit; RCM, red cell mass; BM, bone marrow; EPO, erythropoietin.