Abstract: Objective To explore the predictive value of serum procalcitonin (PCT) to albumin (ALB) ratio and interleukin-23 (IL-23) for the clinical prognosis of sepsis patients. 
Methods Clinical data and follow-up data of 150 patients with sepsis admitted to the hospital from January 2021 to December 2023 were retrospectively collected. They were divided into the death group and the survival group based on the 28-day prognosis. The levels of serum PCT/ALB and IL-23 in patients with different prognosis at admission were compared. COX regression analysis was used to analyze the relationship between clinical prognosis and serum PCT/ALB and IL-23 in patients with sepsis. The interaction of serum PCT/ALB and IL-23 on the prognosis of patients with sepsis was analyzed by interaction analysis. The receiver operating characteristic (ROC) curve was used to analyze the predictive value of serum PCT/ALB and IL-23 for the prognosis of patients with sepsis. 
Results Among 150 sepsis patients with 28-day prognosis, 49 patients died, with a mortality rate of 32.67%. The serum PCT/ALB and IL-23 levels in the death group were higher than those in the survival group at admission ［(60.82±23.28）% vs. （45.35±8.68）%, （425.19±53.48） ng/L vs. (376.12±46.17) ng/L respectively］ (P＜0.05). COX regression analysis showed that the prognosis of sepsis patients was related to the elevation of serum PCT/ALB and IL-23 at admission. Abnormal overexpression of serum PCT/ALB and IL-23 at admission might be a risk factor for mortality in sepsis patients (P＜0.05). There was a positive interaction between serum PCT/ALB and IL-23 levels and mortality in sepsis patients. When both were highly expressed, the risk of mortality was 18.2 times higher than that when both were lowly expressed, and the synergistic effect was 2.435 times higher than the sum of the effects produced by the two alone (SI=2.435). ROC curve was drawn to obtain the area under the curve (AUC), and the results showed that the AUC of serum PCT/ALB and IL-23 alone in predicting the prognosis risk of sepsis patients was 0.726 and 0.763 respectively, which had certain predictive value, while the AUC of combined prediction was 0.872, which was higher than that of the two alone (P＜0.05). Decision curve was drawn, and the results showed that when the threshold was between 0.1 and 0.68, the predictive model combining serum PCT/ALB and IL-23 predicted a better net benefit rate for mortality in sepsis patients than using serum PCT/ALB or IL-23 alone, with a maximum net benefit rate of 0.314 for the combination of the two. 
Conclusion Elevated serum PCT/ALB and IL-23 levels in sepsis patients at admission are risk factors for mortality, and their combined detection has high predictive value for the prognosis of sepsis. 

Key words: sepsis, procalcitonin, albumin, interleukin-23