Association between C-reactive protein-triglyceride glucose index (CTI) and short-term mortality in critically ill patients with sepsis: a prospective cohort study

Background This study aimed to investigate the association between the C-reactive protein-triglyceride-glucose index (CTI) and the risk of in-hospital mortality, 60-day mortality, and 90-day mortality in critically ill patients with sepsis. Methods This was a retrospective cohort study using data from the Medical Intensive Care Unit Marketplace IV (MIMIC IV 3.1) database of patients with sepsis. Participants were divided into four groups based on the quartiles of the CTI index. Multivariate Cox regression was used to assess the association between CTI and mortality, and Restricted Cubic Spline (RCS) analysis was employed to evaluate the dose-response relationship between the CTI index and short-term mortality risk in sepsis patients; Subgroup analysis was conducted using stratified comparisons and interaction tests to assess the consistency of the association between CTI and mortality across different subgroups; the Boruta algorithm was applied to assess the importance of CTI. Kaplan-Meier (KM) curves were used to assess the cumulative survival probability of patients in different CTI groups. In the KM curves, the Log-rank test was used to compare differences between groups (mortality vs. survival). Results A total of 3,693 patients were included. The in-hospital mortality rate, 60-day mortality rate, and 90-day mortality rate were 17.5%, 21.6%, and 23.8%, respectively. In the multivariate Cox regression analysis, when CTI was treated as a continuous variable, each unit increase in CTI was associated with a 23% increase in mortality risk in a model fully adjusted for confounding factors. Additionally, trend tests indicated that the risk of in-hospital mortality, 60-day mortality, and 90-day mortality increased with higher quartiles of the CTI index. RCS analysis confirmed a linear relationship between CTI and the risk of in-hospital, 60-day, and 90-day mortality. Based on subgroup analysis results, in the fully adjusted model, in the majority of the included subgroups, an increase in CTI index was positively associated with an increased risk of in-hospital, 60-day, and 90-day mortality (HR > 1), and this association remained consistent in direction after multivariable adjustment. Notably, no significant interactions were observed (all interaction P values > 0.05). Survival curves also confirmed that patients in the low CTI level group had significantly higher cumulative survival probabilities at 60 days and 90 days compared to those in the high CTI level group. Additionally, the survival probability of critically ill sepsis patients gradually deteriorated from low to high CTI levels. Furthermore, the Boruta algorithm validated that CTI is a key indicator of outcomes in sepsis patients. Conclusion This study confirmed that CTI is linearly associated with in-hospital mortality, 60-day mortality, and 90-day mortality in sepsis patients. Therefore, dynamic monitoring of CTI levels and timely intervention in sepsis patients may be an effective clinical strategy to reduce short-term mortality in sepsis patients.