Sepsis Index as Diagnostic Marker for Sepsis in Adult Intensive Care Unit: A Cross-sectional Study

Abstract Introduction: Sepsis is one of the main causes of death in intensive care units (ICUs) and poses a serious burden on healthcare systems and national economies worldwide. The sepsis index (SI), which is the ratio of neutrophil CD64 (nCD64) to monocyte human leukocyte antigen-DR (mHLA-DR), has been suggested as a useful marker for sepsis because it reflects both inflammation and immune suppression. This study assessed the diagnostic accuracy of the SI and established its optimal cutoff for sepsis detection among critically ill adults in a Vietnamese ICU setting. Materials and Methods: We conducted a cross-sectional study involving 140 adult patients admitted to the ICU between January 2019 and June 2020. Patients were classified into sepsis and nonsepsis groups. The diagnostic performance of the SI was assessed in comparison with individual biomarkers, including nCD64, mHLA-DR, serum procalcitonin (PCT), and white blood cell (WBC) count. Results: The median SI was significantly elevated in patients with sepsis compared to those without (112.95 vs. 10.90; P < 0.001). The SI demonstrated excellent diagnostic performance, with an area under the receiver operating characteristic (ROC) curve (AUC) of 0.92, outperforming PCT (AUC: 0.88), nCD64 (AUC: 0.87), mHLA-DR (AUC: 0.82), and WBC (AUC: 0.58). The combination of SI and PCT had a marginally higher AUC of 0.93, representing the greatest overall diagnostic accuracy. Conclusions: In critically ill adults, the SI proved to be a reliable tool for the early detection of sepsis. Combining the SI with PCT may further enhance diagnostic accuracy.