Abstract Body (Do not enter title and authors here): Introduction: Acute pulmonary embolism (PE) is a life-threatening cardiovascular emergency with a variable course & significant mortality risk. Inflammatory markers have emerged as prognostic indicators in thromboembolic disease, reflecting the interplay between immune activation & vascular injury. The monocyte-to-leukocyte ratio (MLR), derived from routine blood counts, & monocyte chemoattractant protein-1 (MCP-1), a chemokine involved in monocyte recruitment & vascular inflammation, have been associated with cardiovascular & pulmonary conditions. However, the relationship between MCP-1 & MLR, & their roles in predicting mortality in PE, remain underexplored. This study aims to examine the association between MCP-1 & MLR, & evaluate their potential as predictors of in-hospital mortality in patients with acute PE.

Materials and Method: In this prospective study, MLR & MCP-1 levels were assessed for their relationship with in-hospital mortality. Citrated blood samples were collected from 193 patients & MCP-1 was measured using Chemiluminescence Biochip Array, while MLR was calculated from blood count data. Linear regression analysis was used to assess the association between MCP-1 & MLR. Receiver Operating Characteristic (ROC) curve analysis was used to identify optimal cutoff values for mortality prediction. The relationship between MCP-1 & MLR & in-hospital mortality was evaluated using chi-square & logistic regression analysis.

Result: Among 193 patients, 23 (11.9%) died during hospitalization. In patients who died had significantly elevated MCP-1 levels while decreased MLR levels compared to survivors. Linear regression analysis revealed no association between the MCP-1 & MLR and the data has been transformed into MCP-1² (figure 1). ROC curve analysis identified MCP-1 level >127 pg/mL & MLR < -0.057 as optimal cut-off values for predicting mortality (Figure 2). In multivariate regression analysis, MCP-1 >127 pg/mL (OR: 25.31; 95%CI: 3.13-204.55), & MLR < -0.057 (OR: 10.23; 95%CI: 3.50-29.90) found as an independent predictors of in-hospital mortality. The model was adjusted for age, gender, sPESI, & comorbidities, including cancer & cardiopulmonary disease.

Conclusion: Elevated MCP-1 levels & decreased MLR are associated with in-hospital mortality in PE, highlighting the role of inflammation in disease progression. MCP-1 & MLR may serve as accessible prognostic biomarkers for early risk stratification & guide personalized management in acute PE.