The product of fusion gene expression is fusion protein, the normal value should be less than 0.1, mainly refers to two or more genes coding region head-to-tail, and then placed under the control of the same set of regulatory sequences constitute chimeric gene. It is important for the diagnosis of leukemia patients and the evaluation of the treatment effect, as well as the subsequent prognosis and the length of the survival period. A negative test result indicates that the gene mutation is not the cause of the disease. After the diagnosis of the disease is confirmed, reasonable treatment should be chosen as soon as possible.