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

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P value refers to the difference between prefibrotic myelofibrosis and myelofibrosis-fibrotic type;

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P value refers to the difference between prefibrotic myelofibrosis and myelofibrosis-fibrotic type with bone marrow (BM) fibrosis grade 1;

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P value refers to the difference between myelofibrosis-fibrotic type with BM fibrosis grade 1 and with BM fibrosis grade 2 or 3;

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White-blood cell (WBC) count was corrected for the number of circulating erythroblasts;

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Spleen index is the product of the longitudinal by the transverse spleen axis, the latter defined as the maximal width of the organ.