Clinical and laboratory features at diagnosis of 132 patients with prefibrotic myelofibrosis compared with those with primary myelofibrosis-fibrotic type.

§P value refers to the difference between prefibrotic myelofibrosis and myelofibrosis-fibrotic type;§§P value refers to the difference between prefibrotic myelofibrosis and myelofibrosis-fibrotic type with bone marrow (BM) fibrosis grade 1;§§§P value refers to the difference between myelofibrosis-fibrotic type with BM fibrosis grade 1 and with BM fibrosis grade 2 or 3;*White-blood cell (WBC) count was corrected for the number of circulating erythroblasts;**Spleen index is the product of the longitudinal by the transverse spleen axis, the latter defined as the maximal width of the organ.