Clinical significance and prognosis of serum tenascin-C in patients with sepsis

A total of 167 patients with sepsis were included in this study, who were admitted to the Department of Intensive Care Medicine, Seventh People’s Hospital of Shanghai University of TCM, from July 2016 to December 2017. These patients were diagnosed according to the diagnostic criteria proposed by the ACCP/SCCM Consensus Conference [11]. Sepsis was defined as the presence of microbiologically confirmed infections, acute organ failure, and systemic inflammatory response syndrome (at least two of the following parameters: (1) temperature > 38 °C or < 36 °C; (2) heart rate > 90 beats / min; (3) Respiratory rate > 20 beats/min or PaCO₂ < 32 mmHg; (4) white blood cell (WBC) count > 12,000 or < 4000 cells/mm³, or > 10% immature form). Septic shock was defined as septic patients complicated with refractory hypotension (systolic blood pressure < 90 mmHg), and required fluid replacement or vasoconstrictor to maintain blood pressure. The Sepsis-related Organ Failure Assessment (SOFA) score was used to quantitatively estimate the severity of organ damage in patients. These patients received standard treatment, including antibiotics, mechanical ventilation, and fluid resuscitation. All patients were monitored until they were discharged from the ICU or died, with further follow-up for at least 30 days. The control group included 80 gender- and age-matched critically ill patients without sepsis. This study was approved by the ethics committee of Seventh People’s Hospital of Shanghai University of TCM, and conducted in accordance with the Helsinki Declaration. The patient or family signed an informed consent form.

Continuous variables were recorded for all septic patients: age, SOFA score, ICU days, serum creatinine, lactic acid, white blood cell (WBC) count, and platelets. The categorical variables of all patients were recorded: gender, site of infection, ventilator application, and septic shock. The end point was 30-day mortality. Blood samples were taken within 24 h of the ICU admission, kept at 4 °C, and centrifuged at 5000 g for 5 min to separate serum, and stored at − 80 °C. Serum C-reactive protein (CRP), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) levels were determined by enzyme-linked immunosorbent assay (ELISA).

Serum tenascin-C levels in controls and septic patients were measured by ELISA kit (Kamiya Biomedical Company, No. KT-50877, USA), according to the manufacturer’s instructions. The absorbance at 450 nm wavelength was measured by a microplate reader. The serum tenascin-C concentration of each case was determined according to the standard curve established by recombinant tenascin-C at different concentrations.

Of the 167 patients with sepsis admitted to ICU, there were 107 male and 60 female, with a median age of 60 years. The characteristics of septic patients are shown in Table 1. After 30 days of follow-up, 58 patients died and the mortality rate was 34.7%. Patients in the nonsurvivors group had significantly higher age (P = 0.024), SOFA scores (P < 0.001), serum creatinine (P = 0.001), lactic acid (P = 0.008), CRP (P = 0.010), IL-6 (P = 0.010), and TNF-α (P = 0.001) levels compared with survivors. At the same time, the nonsurvivors group had a higher frequency of septic shock and use of mechanical ventilation (Both P < 0.05).

Serum tenascin-C levels (median 56.7 pg/mL) were significantly higher in septic patients than in controls (critically ill patients without sepsis) (median 24.1 pg/mL) (P < 0.001) (Fig. 1a). In patients with sepsis, serum levels of tenascin-C were significantly higher in the nonsurvivors (median 64.9 pg/mL) compared with survivors (median 53.3 pg/mL) (P < 0.001) (Fig. 2b). There was no significant difference in serum tenascin-C between patients with and without ventilator (Fig. 2c), and between patients with and without septic shock (Fig. 2d).

We used Spearman rank correlation test to analyze the correlation between serum tenascin-C and continuous variables. In all patients with sepsis, serum tenascin-C was significantly positively correlated with SOFA score (P = 0.011), serum creatinine (P = 0.006), CRP (P = 0.001), IL-6 (P < 0.001) and TNF-α (P = 0.026) (Table 2).

We used Logistic multivariate regression model to investigate the independent contribution of tenascin-C to the prognosis of patients with sepsis. The results showed that serum tenascin-C levels, together with septic shock, lactic acid and TNF-α, were significantly associated with 30-day mortality (Table 3). ROC analysis determined the serum tenascin-C threshold for 30-day mortality. The area under the curve (AUC) was 0.68 (95% CI = 0.597–0.764; P < 0.001) (Fig. 2a). The threshold of serum tenascin-C was 56.9 pg/mL (sensitivity was 69%, specificity was 60.6%). We also performed ROC analysis on SOFA score to found the difference between survivors and non survivors. The AUC of SOFA score was 0.666 (95% CI = 0.578–0.754; P < 0.001), and the threshold was 12.5 (sensitivity was 55.2%, specificity was 71.6%), this is consistent with those of tenascin-C. We further plotted Kaplan-Meier curve to analyze the effect of high serum tenascin-C on the prognosis of patients with sepsis. Patients with high serum tenascin-C (≥56.9 pg/mL) showed a significantly increased 30-day mortality compared with patients with low serum tenascin-C (< 56.9 pg/mL) (Log Rank = 14.29, P < 0.001) Fig. 2b).