Abstract: Objective To investigate the value of neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and blood platelet count (BPC) in judging the prognosis of adult patients with extensive burns. Methods From January 2012 to December 2018, 99 adult patients with extensive burns who met the inclusion criteria were admitted to Union Hospital of Fujian Medical University, including 76 males and 23 females, aged 18 to 75 (43±13) years. According to the prognosis, the patients were divided into survival group of 79 cases and death group of 20 cases. Their clinical data were retrospectively analyzed by the method of case-control study. The gender, age, total burn area, inhalation injury, use of mechanical ventilation and white blood cell count, neutrophil count, lymphocyte count, and BPC on post injury day (PID) 1, 3, and 7 were collected, and the NLR, PLR, difference value of BPC on PID 3 and PID 1 (ΔBPC3), difference value of NLR on PID 3 and PID 1 (ΔNLR3), difference value of PLR on PID 3 and PID 1 (ΔPLR3), difference value of BPC on PID 7 and PID 1 (ΔBPC7), difference value of NLR on PID 7 and PID 1 (ΔNLR7), difference value of PLR on PID 7 and PID 1 (ΔPLR7) of patients in the two groups were calculated. Data were statistically analyzed with Mann-Whitney U test, independent sample t test, chi-square test to screen the death-related factors of patients. Binary classification single factor and multifactor logistic regression analysis were used to analyze the death-related factors of patients. The receiver′s operating characteristic (ROC) curve of the independent risk factor of death of patients predicting the prognosis of adult patients with extensive burns was drawn, and the area under the curve, the optimal threshold and its sensitivity and specificity were calculated. Results (1) There were statistically significant differences in total burn area and use of mechanical ventilation of patients between the two groups (Z=-2.615, χ²=7.282, P<0.01). (2) On PID 1, there was statistically significant difference in NLR of patients between the two groups (Z=-2.414, P<0.05). On PID 3, there were statistically significant differences in BPC and ΔNLR3 of patients between the two groups (Z=-2.048, -2.780, P<0.05 or P<0.01). On PID 7, there were statistically significant differences in lymphocyte count, BPC, NLR, and ΔNLR7 of patients between the two groups (Z=-2.248, -2.231, -2.641, -3.669, P<0.05 or P<0.01). (3) Binary classification single factor logistic regression analysis showed that the total burn area, mechanical ventilation, BPC and NLR on PID 7, and ΔNLR7 were related to death of patients (odds ratio=1.038, 0.193, 0.990, 1.086, 1.105, 95% confidence interval=1.010-1.067, 0.062-0.598, 0.982-0.998, 1.012-1.165, 1.037-1.178, P<0.05 or P<0.01). Binary classification multifactor logistic regression analysis showed that ΔNLR7 was the independent risk factor of death of adult patients with extensive burns (odds ratio=1.090, 95% confidence interval=1.008-1.178, P<0.05). (4) The optimal threshold of ROC curve of ΔNLR7 for predicting the prognostic death of 97 adult patients with extensive burns was -0.073 4. The sensitivity under the optimal threshold was 65.0%, and the specificity was 78.5%. The area under the ROC curve was 0.776 (95% confidence interval=0.650-0.882, P<0.01). Conclusions Dynamic monitoring of NLR and BPC is of great significance to assist in judging the prognosis of adult patients with extensive burns. ΔNLR7 is an independent predictor of death in adult patients with extensive burns, while PLR can not predict the death of adult patients with extensive burns.