2.2. Degree of bone marrow hyperplasia classification

Histological analysis was performed by a laboratory scientist with 10 years of experience in hematological disorders. Iliac/thoracic bone marrow aspiration was used for cytological analysis. Bone marrow cytosol was examined through a smear and staining process, starting with a low-magnification view of the ratio of mature erythrocytes to nucleated cells to determine the degree of bone marrow hyperplasia, which was generally classified into the following five grades: extremely reduced myeloproliferative, reduced myeloproliferative, active myeloproliferative, markedly active myeloproliferative, and extremely active myeloproliferative.