Table 1. Changes in the WHO Diagnostic Criteria for PMF.

2008 Criteria for PMF	2016 Criteria for pre-PMF	2016 Criteria for overt PMF
Major criteria
MK proliferiferation and atypia with fibrosis (reticulin and/or collagen) or increased marrow cellularity, granulocytic proliferation and decreased erythropoesis in the absence of fibrosis	MK proliferation and atypia without reticulin fibrosis with increased marrow cellularity, granulocytic proliferation and often decreased erythropoesis	MK proliferiferation and atypia with fibrosis (reticulin and/or collagen)
Does not meet WHO criteria for other myeloid neoplasms	Does not meet WHO criteria for other myeloid neoplasms	Does not meet WHO criteria for other myeloid neoplasms
Presence of JAK2V617F or other clonal marker or no evidence of reactive fibrosis.	Presence of JAK2, CALR or MPL mutation or other clonal marker with no evidence of reactive fibrosis	Presence of JAK2, CALR or MPL mutation or other clonal marker with no evidence of reactive fibrosis
Minor criteria
Leukoerythroblastosis	Leukocytosis (⩾11 × 109/L)	Leukoerythroblastosis
Increased serum lactate dehydrogenase	Increased serum lactate dehydrogenase	Increased serum lactate dehydrogenase
Anemia	Anemia (not due to comorbidities)	Anemia (not due to comorbidities)
Palpable splenomegaly	Palpable splenomegaly	Palpable splenomegaly
		Leukocytosis (⩾11 × 109/L)

Abbreviations: MK, megakaryocyte; PMF, primary myelofibrosis.

Changes from the 2008 WHO criteria have been given in bold.