GSTM1 and Absence of circulating granulocytes: To further analyze the risk factors that may be associated with severe pneumonia during leukemia chemotherapy, single suspicious factors in the two groups, including the number of beds in the ward (multiple beds), use of hormones, and neutropenia or agranulocytosis, Hb < 90 g/L, and CRP > 15 mg/L, were screened and then included in the binary logistic stepwise regression equation.