Comparative Study of Biomarkers (PCT, Interleukin-6, Lactate) in Assessing Disease Severity and Organ Dysfunction in Patients with Septic Shock

Objective: To investigate the correlations of procalcitonin (PCT), interleukin-6 (IL-6), and lactate (Lac) with disease severity (assessed by APACHE II score) and organ dysfunction in patients with septic shock, and to compare their predictive values. Methods: We prospectively enrolled 320 patients with septic shock across four clinical centers from June 2023 to March 2025. Patients were divided into a Survival group (n = 248) and a Death group (n = 72) based on 28-day outcomes. Spearman correlation analysis was used to evaluate the relationships of PCT, IL-6, and Lac with APACHE II scores and organ function indicators (creatinine, platelet count, ALT). Results: Lactate showed the strongest correlation with APACHE II scores and was significantly associated with renal dysfunction and coagulopathy. Lactate (Lac) remained the most potent independent predictor of mortality (AUC = 0.884, 95% CI: 0.832-0.936). However, a tri-marker combined model (Lac + IL-6 + NGAL) achieved a superior AUC of 0.942, significantly outperforming any single biomarker (p < 0.001). Conclusion: lactate should be considered a core biomarker for assessing critical illness and prognosis in septic shock.