[Predictive value of plasma exosome count for the prognosis in septic patients].

Objective: To investigate the predictive value of plasma exosome count for the prognosis of patients with sepsis.

Methods: A prospective observational study was conducted. The patients with sepsis admitted to intensive care unit (ICU) of Zhejiang Hospital from November 2020 to December 2021 were enrolled as the study subjects. On the 1st day of admission to the ICU, the patient's gender, age, underlying disease, infection site, mean arterial pressure (MAP) and severity scores were recorded, and venous blood was taken for detecting the blood routine, blood biochemistry, and procalcitonin (PCT), and arterial blood was taken for blood gas analysis, simultaneously, the patient's noradrenaline (NA) dosage was recorded. On the 1st, 3rd, 5th, and 7th day of ICU admission, plasma exosomes were extracted, and the number of exosomes was detected by nanoparticle tracking analyzer. The endpoint of observation was the death of the patient 28 days after admission to the ICU. The differences in baseline data and plasma exosome counts of patients with different 28-day prognosis were analyzed and compared. The Spearman correlation method was used to analyze the correlation between plasma exosome counts and other clinical indicators. Binary multivariate Logistic regression analysis was used to screen the 28-day death risk factors of septic patients. The receiver operator characteristic curve (ROC curve) was plotted to analyze the predictive value of each index on the 28-day death of septic patients. The Kaplan-Meier method was used to analyze the 28-day survival curve.

Results: A total of 26 patients with sepsis were enrolled, of whom 21 survived and 5 died on the 28th day. Compared with the survival group, the patients in the death group had lower MAP, higher sequential organ failure assessment (SOFA) score, acute physiology and chronic health evaluation II (APACHE II) score, white blood cell count (WBC), cardiac troponin I (cTnI), and worse oxygenation. The plasma exosome count on the 1st day of ICU admission in the death group was significantly higher than that in the survival group (×10¹⁵/L: 16.96±9.11 vs. 5.20±2.42, P < 0.05). Subsequently, the plasma exosome counts in both groups continued to decrease, and there was no statistically significant difference between the two groups. Spearman correlation analysis showed that the plasma exosome count on the 1st day of ICU admission in septic patients was significantly positively correlated with SOFA score, APACHE II score, blood lactic acid (Lac), alanine aminotransferase (ALT) and NA dosage (r values were 0.572, 0.585, 0.463, 0.411, 0.696, all P < 0.05), and it significantly negatively correlated with MAP and oxygenation index (PaO₂/FiO₂; r values were -0.392 and -0.496, both P < 0.05). Multivariate Logistic regression analysis showed that plasma exosome count on the 1st day of ICU admission was an independent risk factor for 28-day death in septic patients [odds ratio (OR) = 1.385, 95% confidence interval (95%CI) was 1.075-1.785, P = 0.012]. ROC curve analysis showed that the area under the ROC curve (AUC) of plasma exosome count on the 1st day of ICU admission for predicting 28-day death in septic patients was 0.800 (95%CI was 0.449-1.000); when the optimal cut-off value was 14.50×10¹⁵/L, the sensitivity was 80.0% and the specificity was 100%. According to the optimal cut-off value of 1-day plasma exosome count, the patients were divided into two groups for Kaplan-Meier survival curve analysis, and the results showed that the cumulative survival rate of patients with plasma exosome count < 14.50×10¹⁵/L was significantly higher than that of patients with plasma exosome count ≥ 14.50×10¹⁵/L (Log-Rank test: χ ² = 19.100, P < 0.001).

Conclusions: The plasma exosome count of septic patients is significantly increased on the 1st day of admission to the ICU, which is related to the severity, and can predict the risk of death at 28 days.