Objective To investigate the predictive value of aggregate index of systemic inflammation (AISI), lymphocyte-to-platelet ratio (LPR), neutrophil-to-lymphocyte ratio (NLR) and immune cell counts for clinical prognosis of patients with extremely severe burns.

Methods Clinical data of 101 patients with extremely severe burns admitted to Shandong Provincial Hospital Affiliated to Shandong First Medical University from March 2017 to March 2024 were retrospectively analyzed. According to clinical prognosis, all patients were divided into the survival group (n = 73) and death group (n = 28). The age, gender, total burn area, full-thickness burn area, burn index, inhalation injury, use of mechanical ventilation and lymphocyte count, monocyte count, neutrophil count, platelet count on days 1, 3 and 7 after hospital admission were collected, and AISI, LPR and NLR were calculated. The data were statistically analyzed to assess the predictive value of these indexes for clinical prognosis of patients with extremely severe burns. Cox proportional hazards regression model was used to analyze the correlation between these indexes and clinical prognosis. The receiver operating characteristic (ROC) curve of the independent risk factors for death in patients with extremely severe burns, and the area under the ROC curve (AUC) was calculate. The optimal cut-off value and its corresponding sensitivity and specificity were also obtained. According to the optimal cut-off value, all patients were divided into two groups. Kaplan-Meier method was used to delineate the survival curve. The predictive value of each index for the 90-d survival rate of patients with extremely severe burns was evaluated.

Results The total burn area, full-thickness burn area, burn index, inhalation injury and use of mechanical ventilation in the death group were more severe than those in the survival group (all P ＜ 0.05). In the death group, lymphocyte count on days 1 and 7, monocyte count on days 1 and 7, neutrophil count on day 1, AISI on days 1 and 7, LPR on day 3 and 7, NLR on day 3 were significantly higher compared with those in the survival group (all P ＜ 0.05). Cox proportional hazards regression model showed that monocyte count on days 1 and 7, neutrophil count on day 1, AISI on day 1, LPR on day 3 and 7, lymphocyte count on day 7 were the risk factors for death of patients with extremely severe burns (all P ＜ 0.05). After adjustment of burn index, inhalation injury and use of mechanical ventilation, AISI, monocyte count, neutrophil count on day 1 and NLR on day 3 were found to be the independent risk factors for 90-day mortality in patients with extremely severe burns (all P ＜ 0.05). The AUC of AISI, AMC, ANC on day 1 and NLR on day 3 for predicting the outcome of death of patients with extremely severe burns were 0.691 (95%CI: 0.570-0.831), 0.718 (95%CI: 0.604-0.832), 0.721 (95%CI: 0.609-0.832), 0.641 (95%CI: 0.524-0.758). Kaplan-Meier survival analysis showed poor prognosis in patients with higher AISI, monocyte count, neutrophil count on day 1 and NLR on day 3 (all P ＜ 0.05).

Conclusion AISI, monocyte count, neutrophil count on day 1 and NLR on day 3 are the independent risk factors of clinical prognosis, which can be used as reliable indexes to assess clinical prognosis of patients with extremely severe burns.