OBJECTIVE: Leukemia-related fusion gene testing has gained acceptance as a diagnostic, prognostic and MRD test for leukemia. Gene rearrangements in mixed lineage leukemia (MLL) suggest a poor prognosis. In this study, we applied multiple nested reverse transcription-polymerase chain reaction to detect MLL-associated fusion genes in patients with acute myeloid leukemia. The incidence, clinical characteristics and prognostic features of rearrangements of MLL genes in patients with acute myeloid leukemia were reported. Yang Hua, Department of Hematology, Beijing 301 Hospital, Beijing, China METHODS: This study retrospectively analyzed. 433 AML patients from the General Hospital of the Chinese People’s Liberation Army from April 2008 to November 2011 were screened for the incidence of 11 MLL gene rearrangements in 433 AML patients by applying multiplex nested PCR. These 11 MLL gene rearrangements included (MLL-PTD, MLL-AF9, MLL-ELL, MLL-AF10, MLL-AF17, MLL-AF6, MLL-ENL, MLL-AF1Q, MLL-CBP, MLL-AF1P, MLL-AFX1). We analyzed the prognostic characteristics of AML patients with 68 MLL gene rearrangements in 433 AML patients with a positive rate of 15.7%. 24 received allogeneic peripheral hematopoietic stem cell transplantation (Allo-HSCT) (3 lost to follow-up). 34 patients received chemotherapy of which (6 lost to follow-up) and 8 chemotherapy for less than 4 cycles. 2 patients underwent autologous hematopoietic stem cell transplantation (Auto-HSCT) and 8 patients abandoned treatment. Twenty-one patients in the transplantation group and 20 patients in the chemotherapy group were compared for differences in OS and DFS between the two groups, and prognostic factors were analyzed using univariate and multifactorial methods. Results: 24 cases of MLL gene rearrangement occurred in the highest number of M5 cases (35.3%). The number of positive cases and positivity rate of the above 11 genes were 21 (4.84%), 15 (3.46%), 10 (2.31%), 8 (1.85%), 3 (0.69%), 3 (0.69%), 3 (0.69%), 2 (0.46%) 1 (0.23%), 1 (0.23%), 1 (0.23%), 1 (0.23%), respectively. In patients with positive MLL fusion genes, the median follow-up was 29 months. The complete remission CR rate was (35/41) 85.4%, and the first course remission rate (CR1) was (16/41) 39%. The overall relapse rate was (15/41) 36.6%, with a 28.6% relapse rate in the transplantation group (6/21) and a 40% relapse rate in the chemotherapy alone group. OS was (57.4±5.9 months & 21.0±2.1 months in the transplantation group and chemotherapy alone group, respectively, P<0.01). The transplantation group had a superior survival advantage over the chemotherapy alone group in terms of OS (3-year OS: 76 ± 10% & 32 ± 11%, p < 0.01); there was no significant superiority in the dfs transplantation group compared with the chemotherapy alone group (3-year dfs:="" vs.="" p="">0.05). Univariate and multifactorial analysis, choice of treatment regimen (transplantation or chemotherapy) (RR = 0.216, 95% CI 0.125-0.893, p = 0.001). Platelet count at onset (>50×109 /l or ≤50×109 /l) (RR = 0.221, 95%CI: 0.073-0.674; P=0.008). CR or not (RR = 0.358, 95%CI: 0.131-0.981; P=0.046) was an independent prognostic factor for OS and Patients with transplantation, platelets >50×109 /l and CR had a better prognosis. Extramedullary involvement, with leukocytes >10×109/l at onset, did not affect OS. platelet count (>50×109 /l or ≤50×109 /l) at onset (RR = 0.154,95% CI: 0.033-0.714; P=0.017) and whether extramedullary involvement (RR = 4.447,0.95% CI: 1.491-13.263; P=0.007) were independent prognostic factors for DFS and Patients with thrombocytopenia and extramedullary involvement were prone to relapse. After 4 cycles of chemotherapy or pre-transplantation testing of 22 patients with minimal residual disease MRD (MRD) negative and 19 patients with MRD positive, the OS and DFS of the two groups were compared and MRD negative patients were found to have a better OS (P = 0.05). We found that the MRD-negative patients had better OS (P = 0.001) and DFS (P = 0.001) CONCLUSION: The application of multiplex nested PCR method for screening MLL genes in AML patients is convenient, fast, economical and accurate. In patients with MLL gene rearrangement in AML (Allo-HSCT) can significantly prolong OS, and better prognosis and long-term survival can be obtained. Platelet count at onset was an independent prognostic factor for OS and DFS, CR was an independent prognostic factor for OS, and extramedullary involvement was an independent prognostic factor for DFS. MRD-negative patients had a better prognosis. Patients with MLL gene rearrangement AML with thrombocytopenia at onset had a poor prognosis.