Sepsis emerges as a significant contributor to morbidity and mortality post-PCNL, particularly affecting elderly, immunocompromised, and critically ill individuals [4, 19, 20]. The prevalence of septic shock following PCNL has shown a notable rise over the past years, escalating from 1.2% in 1999 to 2.4% in 2009, marking a twofold increase within a 17-year period [21]. Studies have underscored the pivotal role of prompt recognition and proactive management of sepsis and septic shock in enhancing patient outcomes and diminishing mortality rates [4, 20, 22].

In 1991, the American College of Chest Physicians (ACCP) and the Society of Critical Care Medicine (SCCM) convened a consensus meeting, introducing the concepts of “systemic inflammatory response syndrome” (SIRS), “sepsis,” and “septic shock” based on clinical and laboratory parameters [4, 5, 20, 23]. SIRS has been widely used in various medical institutions, but its broad inclusion criteria, low specificity, and potential for overdiagnosis have led to the proposal of different scoring systems [6, 24]. Among them, the National Early Warning Score (NEWS) is more widely applied. However, due to different hospitals having different evaluation criteria for accurate issues, there is a lack of equal communication of patient conditions between different medical institutions, and there is also no unified training for healthcare personnel [12, 16]. In order to establish a standardized system, NEWS was proposed in 2012 based on the NHS Early Warning Score. It has since been widely used in ICUs, emergency departments, and other medical settings to assess patients general conditions and determine whether they need escalated medical care and nursing [16]. Nevertheless, the efficacy of NEWS in improving patient care lacks empirical support, with existing studies being predominantly observational and establishing a correlation between score deterioration and prognosis, as well as early detection of patient deterioration. Notably, the accuracy of postoperative NEWS assessment on the day of surgery is compromised by surgical stress and intraoperative medication use [6].

In addition, qSOFA scores are widely used in the identification of sepsis patients. qSOFA scores are a simplified version of the SOFA score, which evaluates six organs or systems – respiratory, coagulation, liver, cardiovascular, central nervous, and renal – by quantifying the function of each organ with scores [15]. The qSOFA score quickly identifies septic patients by assessing blood pressure, respiratory rate, and state of consciousness [15]. Nevertheless, the qSOFA score is constrained by its low sensitivity. Two meta-analyses have revealed that its ability to predict mortality in suspected infection patients was below 50% [25, 26]. This lack of sensitivity implies that a significant proportion of high-risk sepsis patients may go undetected, hampering timely intervention for sepsis [27].

One central event in the pathophysiological cascade of sepsis is the excessive systemic release of pro-inflammatory cytokines in response to microbial invasion, such as IL-6 [7, 8]. IL-6 is a multifunctional cytokine that regulates immune responses and is considered an endogenous pyrogen that causes fever in infected patients [8, 28]. After infection and inflammation occur, IL-6 is generated first and its levels rapidly increase, reaching a peak within 2 h [8, 17]. The elevated levels of IL-6 are consistent with the severity of infection and induce the increase of PCT and C-reactive protein (CRP) levels, which start to rise 2 h and 6 h after infection, respectively [7, 10, 29]. The serum PCT value reaches its peak 12 to 24 h after infection [10, 30, 31]. As an upstream inflammatory factor of PCT, IL-6 has a more timely response, and the studies have shown that high levels of IL-6 indicate poor prognosis in septic patients. However, due to the unclear timing of inflammatory triggers in departments such as the ICU, the use of IL-6 in predicting infections is somewhat limited.

This study considers surgery as an inflammatory trigger and measures serum IL-6 levels two hours after surgery. At this time, the inflammation is in the early stages, making it possible to predict sepsis in the early stages of infection. Additionally, IL-6 is a laboratory marker that provides rapid and relatively objective results, with high sensitivity. This study evaluated the predictive value of three scoring systems by measuring their ROC curves and AUC values. The value of AUC for IL-6 was 0.993, for SIRS was 0.928, and for NEWS was 0.824. The AUC for IL-6 was statistically different from the AUC for SIRS and NEWS. Compared to NEWS and SIRS, IL-6 was less affected by surgical stress and intraoperative medications, and had higher specificity in prediction.

There were two main limitations of this study. First, it was a single institutional retrospective study design. Since all the data were from clinical sources, there may be potential bias. Second, the sample size of this study was small. In the next study, we will expand the sample size and further confirm the conclusions through prospective studies.