Objective To investigate the utility of combined test of neutrophil CD64 and C-reactive protein(CRP)for early diag-nosis of burn sepsis.Methods A prospective study was conducted in 76 hospitalized burn patients,including three groups:burn sepsis(n=27),local infection(n=31)and controls without bacterial infection (n=18)based on their diagnosis.Blood samples were collected within 24-48 h after hospital admission for analysis of neutrophil CD64,CRP,white blood cell count (WBC), neutrophils percentage (N)by flow cytometry,and bacterial culture.These parameters were re-evaluated for the patients in sepsis group 7 and 14 days after antibiotic therapy.Results Neutrophil CD64,CRP,WBC and N were significantly higher in sepsis patients than the corresponding values in the patients with local infection or control patients (P < 0.01 ).Neutrophil CD64 and CRP in the patients with local infection were significantly higher than those in the control patients without bacterial infection (P < 0.01).Neutrophil CD64 was positively correlated to CRP.Neutrophil CD64 and CRP decreased 7 days after an-tibiotic therapy,but the difference was not statistically significant compared to the pretreatment levels.Neutrophil CD64 and CRP decreased significantly 14 days after antibiotic therapy compared to the pretreatment levels (P < 0.01),but still higher than the levels in the control group.The receiver operating characteristic (ROC)curve of CD64 + CRP combined test,CD64, CRP,WBC,N for detecting bacterial infection showed an area under curve (AUC)of 0.952,0.923,0.904,0.756 and 0.728,respectively.Conclusions Neutrophil CD64 is useful in early diagnosis of burn sepsis.The expression of neutrophil CD64 does not have significant difference between gram-positive and gram-negative bacterial infections.Combined test of neutrophil CD64 and CRP can improve the efficiency for diagnosis of burn sepsis.