The main clinical focus is on the number of platelets, and the width of platelet distribution can also be referred to at the same time. Platelet distribution width mainly refers to the width of platelet volume distribution, the coefficient of variation of platelet volume, if the platelet distribution width becomes smaller, it indicates that the platelet volume becomes smaller. In the case of bone marrow failure diseases, aplastic anemia, MDS myelodysplastic syndrome, myelofibrosis and other bone marrow failure diseases, the ability of bone marrow megakaryocytes to produce platelets is reduced and platelet volume may decrease. When performing routine blood tests, a calculated decrease in platelet distribution width often indicates a decrease in bone marrow hematopoietic function.