Criteria	WHO 5th Edition [7]	ICC [6]
Leukocytosis	Present, must be ≥25 × 109/L, regardless of mutations	≥13 × 109/L for CSF3R- mutated cases, ≥25 × 109/L in non-CSF3R mutated cases
Marrow cellularity	Hypercellular, neutrophils + banded neutrophils constitute ≥80% of the white blood cells
Neutrophil precursors	<10% of the WBCs
Neutrophilia	Persistent for 3 months or more, splenomegaly with no identification of reactive causes in mutation negative cases
Dysplasia	Not present
Monocytes	<10% of peripheral blood monocytes
Rule out	Chronic Myeloid Leukemia (CML), polycythaemia vera, essential thrombocythaemia, or primary myelofibrosis, myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions and exclusion of reactive neutrophilia.