Table 2.

Summary of IWG Criteria for PPV-MF and PET-MF

Post-Polycythemia Vera Myelofibrosis (PPV-MF)	Post-Essential Thrombocythemia Myelofibrosis (PET-MF)
Required criteria
Prior diagnosis of PV according to WHO criteria. Bone marrow fibrosis ≥ grade 2	Prior diagnosis of ET according to WHO criteria. Bone marrow fibrosis ≥ grade 2
Additional criteria (two required)
Anemia or loss of phlebotomy requirement Leukoerythroblastosis New splenomegaly or ≥5 cm increase in spleen size Development of at least one constitutional symptoma	Anemia and decrease ≥2 g/dL in hemoglobin level Leukoerythroblastosis New splenomegaly or ≥5 cm increase in spleen size Increased LDH Development of at least one constitutional symptoma

Notes: ^aConstitutional symptoms include > 10% of weight loss in six months, night sweats and unexplained fever (> 37.5 °C). Data from Barosi et al.⁵

Abbreviations: IWG, International Working Group; WHO, World Health Organization; LDH, lactate dehydrogenase.