PVSG and WHO vs European Clinical, Molecular and Pathological Criteria for prefibrotic myeloproliferative neoplasms

Table 1 Blood and bone marrow features in one prospective study of Thrombocythemia Vera Study Group-defined essential thrombocythemia and one retrospective study of Polycythemia Vera Study Group defined essential thrombocythemia at platelet counts above the upper limit of normal

Ref.	Michielset al[11]	Lengfelderet al[30]
Type of study	Prospective 1975-1985	Retrospective 1975-1995
Diagnosis ET	TVSG criteria	PVSG criteria
Inclusion criterion	ET	ET	Tentative diagnosis
Platelet count × 109/L	> 400	> 350	WHO-ECMP
Number of ET patients	30	143
Platelets × 109/L range	420-1500	< 350-> 000
Below 600	13%	29%	Early latent ET
Between 600-1000	54%	45%	Fits with ET
Above 1000	33%	26%	Fits with ET
Leukocytes
Above 12 × 109/L	10%	51%
Hemoglobin
Below 16 g/dL	-	80%
Below 17 g/dL	-	100%
Above 16 g/dL	-	20%	Fits with PV
Splenomegaly
No	63%	56%
Yes	37%	44%
Spleen size on echogram (cm)
n < 12/12-15/> 15	2019/8/3	-
Bone marrow biopsy
Normal cellularity	17 (57%)	52%	Fits with true ET
Increased cellularity	13 (43%)	60%
Increased erythropiesis	13 (43%)	17%	Fits with early PV
Increased granulopiesis	0	45%	Fits with CMGM
Myelofibrosis	No	No

Essential thrombocythemia (ET) according to Polycythemia Vera Study Group (PVSG) criteria appears to be a spectrum of normocellular ET, prodromal polycythemia vera (PV) and ET due to megakaryocytic, granulocytic myeloproliferation or ET associated with chronic or primary megakaryocytic granulocytic myeloproliferation (CMGM/PMGM) when diagnostic World Health Organization and European Clinical, Molecular and Pathological (WHO-ECMP) bone marrow features are applied. TVSG: Thrombocythemia Vera Study Group.