Plasma level of neutrophil extracellular traps in septic patients and its clinical significance: a prospective observational study

Abstract

To investigate the changes of neutrophil extracellular traps (NETs) level in plasma of sepsis patients and judge its clinical value for early diagnosing of sepsis. A prospective observational study was conducted. The patients after surgery aged > 18 years and expected to stay in the ICU > 24 hours admitted to intensive care unit (ICU) of the First Affiliated Hospital of China Medical University from November 2014 to February 2015 were enrolled. According to the criteria of sepsis diagnosis in 1991, patients were divided into non-sepsis group and sepsis group. The healthy people who taken a physical examination were enrolled in the healthy control group. 3 mL peripheral venous blood was collected at 1 hour after admission to ICU. A fasting blood was collected in the healthy control group in the morning. The plasma free DNA (cf-DNA/NETs) was determined by using the fluorescence microplate reader, white blood cell (WBC), neutrophil ratio (NEU), procalcitonin (PCT), C-reactive protein (CRP) in peripheral blood of the patients were detected, and acute physiology and chronic health evaluation II (APACHE II) and sequential organ failure assessment (SOFA) scores were calculated. The correlation between plasma NETs and the risk factors in sepsis patients was analyzed by Spearman correlation analysis. The value of cf-DNA/NETs and WBC level in the diagnosis of sepsis was analyzed by using the receiver operating characteristic curve (ROC). Twenty-three sepsis patients, 20 non-sepsis patients, and 22 healthy persons were enrolled. There were no differences in baseline variables including gender and age among three groups, which indicated baseline data equalization. The plasma concentration of cf-DNA/NETs in sepsis group was significantly higher than that in non-sepsis group and healthy control group (μg/L: 453.44±185.37 vs. 188.35±29.66, 203.83±43.25, both P < 0.05), and there was no significant difference between last two groups (P > 0.05). WBC, NEU, PCT, CRP, APACHE II and SOFA score in sepsis group were significantly higher than those of non-sepsis group [WBC (×109/L): 9.52±5.51 vs. 5.97±2.28, NEU: 0.787±0.110 vs. 0.655±0.067, PCT (mg/L): 7.14 (3.60, 13.29) vs. 6.07 (3.57, 7.91), CRP (mg/L): 64.44±13.14 vs. 27.00±19.47, APACHE II: 10.25±4.92 vs. 6.00±1.22, SOFA: 6.0±5.1 vs. 5.0±1.2, all P < 0.05]. Correlation analysis showed that the level of NETs had no obvious correlation with gender, age, WBC, NEU, PCT, CRP, APACHE II and SOFA scores (r value was 0.322, 0.262, 0.194, 0.312, 0.227, 0.454, 0.433, 0.333, respectively, all P > 0.05). The area under the ROC curve (AUC) of plasma cf-DNA/NETs for the diagnosis of sepsis was 0.981. When the cut-off value of plasma cf-DNA/NETs was > 257.96 μg/L, the sensitivity was 91.3%, specialty was 95.2%, and Youden index was 0.865. AUC of WBC in the diagnosis of sepsis was 0.663. When the cut-off value of WBC was > 6.0×109/L, the sensitivity was 78.3% and specificity was 25.0%. The plasma cf-DNA/NETs levels increased significantly in sepsis patients. In the diagnosis of sepsis, plasma NETs levels had better advantages over WBC. NETs can be used as a biomarker for early diagnosis of sepsis.