This paper is the first to investigate suPAR levels combined with the qSOFA score in patients with sepsis based on Sepsis-3. We developed a simple risk stratification system for patients with sepsis by taking into consideration qSOFA score and the serum biomarker suPAR .
In the current study, we found that suPAR performed better predictive value for 28-day hospital mortality of patients with sepsis or septic shock than commonly used biomarkers, such as CRP and PCT. Moreover, the predictive abilities were slightly improved when suPAR combined with qSOFA scores.
Sepsis is a physiopathological process rather than a specific syndrome[17], and it is too complex and cannot be simply described by a single measure. For this reason, neither clinical nor biological markers have been demonstrated to be perfect prognostic tools. Severity scores such as the Acute Physiology and Chronic Health Evaluation (APACHE) II score and Sequential Organ Failure Assessment (SOFA) score are the gold standard for severity assessment of critically ill patients [18]. However, the assessment of scoring systems to guide decision making in sepsis is sophisticated and is not readily available in pre-ED.
Recently, some authors reported that qSOFA could be a useful tool in hospital ED settings outside the intensive care unit. In this case, qSOFA could predict death of sepsis patients, but it could be overcome by rapid and accurate laboratory diagnostic tests [19]. qSOFA score with a cut-off value of ≥ 2 showed a low sensitivity and high specificity. Our study found that the AUC of qSOFA alone was 0.832 for 28-day mortality. Furthermore, the present study showed that qSOFA alone has a low post-test probability that increased significantly when associated with PCT [7]. In the analysis by Giamarellos-Bourboulis et al [20], qSOFA score had inadequate sensitivity for early risk assessment.
Classical biomarkers have not been shown to be better than generic scores in predicting outcome in septic patients [21]. Many studies focus on the prognostic value of suPAR which has been proposed as a biomarker for the risk of death. Early increase in suPAR has also been reported to be strongly associated with risk of in-hospital-, 30-day-, and 90-day mortality in sepsis patients and correlated with sepsis severity [22–24]. In our study, we found that serum suPAR levels were significantly higher in the septic shock and non-survivor groups than in the sepsis and survivor groups. Our results are consistent with those of previous studies. The AUC for suPAR in predicting in-hospital mortality ranges from 0.67 to 0.84 [17, 23, 25, 26]. Several studies have showed the superiority of suPAR over conventional biomarkers such as CRP and PCT [13, 25, 27–29]. Consistent with previous reports, the AUC for suPAR of out study to predict mortality was 0.646 which was also better than CRP and PCT(0.483 vs 0.470).
Kaplan–Meier curves showed that suPAR ≥ 1382 pg/mL was associated with significantly higher 28-day mortality risk; this threshold value is identical to that reported in prior studies [17, 30].
Based on the above analysis, we indicate that suPAR may provide a promising prognostic biomarker in sepsis.
There were several studies of suPAR combined with other indicators or qSOFA combined with other indicators in prediction of mortality of infected patients. Kofoed et al. [31] demonstrated that suPAR levels had a better prognostic value than PCT and CRP, equal to that of the admission SOFA score and almost as good as that of the Simplified Acute Physiology Score( SAPS ) II score and that the combination of suPAR and age had a better prognostic value than the SAPS II score alone. Julián-Jiménez et al found that qSOFA scores achieved better results for 30-day mortality than systemic inflammatory response syndrome, and that qSOFA plus mid regional pro-adrenomedullin [MR-proADM] could increase the predictive power in elderly patients visit ED due to infections than qSOFA alone[32].
There has been no report on the prognostic value of combining suPAR and qSOFA. We propose to improve prognostication of 28-day mortality of sepsis by using the qSOFA score combined with suPAR, a serum biomarker that is easily performed on-site and provides information within 1 h [33]. Our results show that the AUC of the combination of suPAR and qSOFA was better than that of qSOFA or suPAR alone and combined model(suPAR + CRP and suPAR + PCT).
There is a fact that suPAR is a non-specific inflammatory marker and a strong and independent predictor of mortality in patients with CHF[34], Data presented in Tabel 1 showed that non-survivors compared with survivors included more patients with coronary heart disease (41.5% vs. 11.9%). So we assessed the ROC of the combined model and single model that was no significant difference between two groups stratified by CHD and without CHD (P = 0.447,data was not shown).
There were some limitations of ROC curves in evaluating biomarkers [35]. Thus, the net reclassification improvement (NRI) was applied to estimate the strength of associations in this study .The NRI captures the relative improvement in classification associated with the additional predictive variable, while explicitly balancing trade off between changes in sensitivity and specificity. NRI is the sum of 2 percentages with different denominators and hence, is reported as a proportion (possible range, − 2.0 to 2.0)[36].Although serum suPAR did not significantly increase the AUC of the basic qSOFA, a model containing suPAR in addition to qSOFA had a continuous NRI of 11% (95% CI: 3.5–18.5%, p = 0.004). In other words, the addition of suPAR to the clinical predictive model (qSOFA) could improve its discrimination and predictive value for outcomes than qSOFA alone.