Low‐grade inflammation for predicting severe acute pancreatitis in patients with hypertriglyceridemic acute pancreatitis

We aimed to evaluate the association between low‐grade inflammation (LGI) and the severity of hypertriglyceridemic acute pancreatitis (HTG‐AP).

The global incidence of acute pancreatitis (AP) is 13-45 per 100 000 population, among which that of hypertriglyceridemic acute pancreatitis (HTG-AP) has been gradually increasing. 1 Recent studies have revealed that HTG-AP accounts for 2%-5% of all AP cases in the United States.
Following gallstones and alcohol abuse, HTG is the third most common cause of AP. 2 Previous studies have reported that the incidence of HTG-AP has surpassed alcohol abuse and become the second leading cause in China. 3Up to 20% of individuals with AP develop severe disease, manifesting as systemic inflammatory response syndrome (SIRS), pancreatic edema, pancreatic necrosis, and in the worst case, multiorgan failure (MOF), resulted in a mortality of 10%-30%. 2 The pathogenesis of HTG-AP remains unclear.Previous studies have suggested that compared to AP caused by other etiologies, HTG-AP is more severe and may more frequently lead to complications due to the intense inflammatory response induced by massive blood triglyceride (TG). 4RS has been recognized as the first stage of severe acute pancreatitis (SAP), during which MOF and death may occur. 5Inflammation plays a fundamental role in HTG-AP; however, specific, quantifiable indicators that can accurately assess inflammation in AP are lacking.
Low-grade inflammation (LGI) has been proposed as an underlying pathophysiological mechanism linking metabolic disorders, including oxidative stress, obesity, diabetes mellitus, and dyslipidemia, to an increased risk of chronic degenerative disease. 6,7It has also been regarded as a common pathogenic denominator in age-related diseases. 8C-reactive protein (CRP), platelet (PLT) count, and white blood cell (WBC) count have been identified as indicators of LGI. 9,10Recently, the neutrophil-tolymphocyte ratio (NLR) has been shown to indicate early inflammatory cellular response. 11,12However, several studies [13][14][15][16][17] on the relationship between CRP or NLR and the severity of HTG-AP have yielded inconsistent results, with some revealing significantly positive association and others showing no association.Notably, these indicators do not change separately in a patient, and a comprehensive approach considering their potential synergistic effects may provide a better understanding of LGI status.A study 18 including 117 865 individuals demonstrated that a high non-fasting TG level was associated with both high concentrations of inflammatory markers and a high risk of AP, and that the relationship between TG and AP was possibly mediated partly by LGI even after adjusting for inflammatory markers.However, the effect of LGI on the severity of HTG-AP has not been studied yet.
In this study, we aimed to evaluate the association between a composite LGI score, which was derived from four individual LGI indicators, and disease severity in patients with HTG-AP.Data collected from the electronic database records included age, gender, comorbidities, clinical manifestations, Marshall scores, laboratory test results and imaging findings.All the laboratory measurements were performed within 24 h after their admission.

| Measurement of LGI
Peripheral blood samples were obtained from each patient within 24 h after their admission.The levels of CRP, WBC, PLT, and NLR were measured for the calculation of the LGI score.To calculate the LGI score, 10 tiles of the level of each biomarker (CRP, WBC, PLT, NLR) were generated.For all the four components, being in the highest deciles (7-10) was given a score of 1 to 4, while being in the lowest deciles (1-4) was negatively scored from À4 to À1.In addition, the middle deciles (5 and 6) were scored as 0 point.The LGI score was calculated as the sum of the four components and ranged between À16 and 16.The patients were categorized into four quartiles based on their LGI score, ie, Q1 (LGI score ≤À5), Q2 (LGI score ranged À4 to À1), Q3 (LGI score 0-4), and Q4 (LGI score >4).

| Definitions
AP was diagnosed according to the Revised Atlanta Classification 19 when at least two of the following three criteria were met: (a) abdominal pain consistent with AP (acute onset of a persistent, severe, epigastric pain often radiating to the back); (b) levels of amylase and/or lipase at least three times over the upper limit of normal (ULN); and (c) characteristic findings of AP on imaging examinations including contrast-enhanced computed tomography, magnetic resonance imaging, or transabdominal ultrasonography.HTG-AP was considered in patients with AP when their serum TG level was ≥11.3 mmol/L, or between 5.65 mmol/L and 11.3 mmol/L with lactescent serum on admission. 20e severity of AP was graded as mild acute pancreatitis, moderately severe acute pancreatitis (MSAP), and severe acute pancreatitis (SAP) according to the Revised Atlanta classification. 19MAP was defined by the absence of organ failure and local or systemic complications.MSAP was defined by the presence of transient (≤48 h) organ failure or local or systemic complications in the absence of persistent organ failure.While SAP was defined by persistent (>48 h) organ failure.Organ failure referred to a modified Marshall score ≥2 for any of the cardiovascular, respiratory and renal systems. 19Patients in our study were divided into the MAP group and the SAP group, respectively, the latter of which included both MSAP and SAP.

| Clinical characteristics of patients with HTG-AP
Between April 2012 and March 2021, 371 patients with HTG-AP were diagnosed at the Department of Gastroenterology, Fujian Provincial Hospital.60 patients were excluded because their laboratory test was performed over 24 h after admission.Finally, a total of 311 hospitalized patients who met the eligibility criteria were retrospectively included (Figure 1).
Compared with patients with the first quartile of LGI scores, those with higher LGI scores had a lower rate of MAP (P < 0.001) and a higher improved Marshall score (P = 0.010) (Table 1).

| Clinical characteristics of patients with HTG-AP stratified by the severity of AP
According to the severity of AP, the patients were divided into the MAP and SAP groups, the latter of which included both patients with MSAP and those with SAP.As shown in the Table 2, the SAP group had a higher median improved Marshall score (1.00 vs 0, P < 0.001), higher

| Prediction of HTG-AP severity
Univariate logistic regression analysis showed that patients with the fourth quartile of the LGI score had a significantly higher risk of developing MSAP and SAP compared to those with the first quartile of the LGI score (OR 21.925, 95% CI 5.014-95.867,P < 0.001; Table 3).
Furthermore, the LGI score showed the highest AUROC (0.7737) that outperformed its individual components, including CRP (0.7679), WBC (0.6751), PLT (0.5724) and NLR (0.7072) alone, indicating the potential of LGI score as a predictor of disease severity in patients with HTG-AP (Figure 2).

| DISCUSSION
LGI was conceived as a subclinical condition (systemic or local, often chronic) characterized by increased levels of plasmatic and/or cellular biomarkers of inflammation without any apparent clinical signs. 9The LGI score has been extensively investigated in studies involving various chronic conditions, such as cardiovascular disease, cancer, metabolic disorder, and chronic obstructive pulmonary disease, showing that it is associated with an increased risk of these chronic diseases. 21However, few studies have been conducted on LGI and acute inflammatory diseases.To the best of our knowledge, this study is the first to explore the association between the severity of HTG-AP and the LGI score.
we investigated the value of LGI in evaluating the severity of HTG-AP, and found that a high LGI score (P = 0.006) and low calcium (P = 0.047) were risk factors for MSAP and SAP according to the multivariate logistic regression analysis.
Since patient prognosis and clinical intervention of HTG-AP differ largely between MAP and SAP, early prediction of disease severity is vital for disease management.Individual clinical, laboratory, and radiological indicators as well as various scoring systems have been proposed for the prediction of AP severity.The guidelines have suggested persistent organ failure lasting for at least 48 h as a predictor for SAP. 28In HTG-AP, other recognized risk factors for the development of SAP include elevated CRP, WBC, NLR, TG, creatinine, body mass index, and serum ionized calcium, 15,16,29,30 although their clinical utilities are still limited due to the low predictive values. 31,32Many studies have focused on one single indicator as a risk factor for SAP rather than utilizing a combination of selected indicators.At present, no single marker has been found to accurately predict SAP.CRP, WBC, NLR, and PLT can be measured at disease onset; therefore, LGI is relatively easy to be obtained in the early stage of disease compared with persistent organ failure.
In our study, the fourth quartile of LGI score (OR 21.925, 95% CI Moreover, the LGI score showed the highest AUROC (0.7737) compared to its single components.The ROC curve is an effective method to evaluate the diagnostic performance of the tests.The AUROC of 0.9 to 1 is considered "excellent", 0.8 to 0.9 is "good", 0.7 to 0.8 is "fair", 0.6 to 0.7 is "poor", and 0.5 to 0.6 is "fail". 33The results indicated that a higher LGI score was associated with an increased risk of SAP in patients with HTG-AP.Previous studies 15,16 The receiver operating characteristic curves of the low-grade inflammation (LGI) score and its individual components, including C-reactive protein (CRP), platelet (PLT), white blood cell (WBC), and neutrophil-to-lymphocyte ratio (NLR), for predicting severe acute pancreatitis in patients with hypertriglyceridemic acute pancreatitis.The area under the receiver operating characteristic curve of the LGI score (0.7737) was higher than that of any single component.
In the present study the predictive role of LGI score was not compared with that of the improved Marshall score, which is the gold standard for distinguishing the severity of HTG-AP. 19Our results showed a significant association between LGI and severity of HTG-AP; however, PLT did not appear to be associated with the severity of HTG-AP.We postulate that the association between LGT and the severity of HTG-AP might be weakened by PLT, which needs to be verified in future studies.
To the best of our knowledge, this is the first study investigating the association between the LGI score and the severity of HTG-AP.
One of the strengths of this study was the high accuracy in the data, which was achieved through rigorous eligibility criteria of the patients and diagnostic criteria for HTG-AP.
There were some limitations to this study.First, this was a retrospective study conducted at a single center with limited sample size.Therefore, selection bias could not be avoided and might have limited the generalizability of the findings.Large prospective studies are needed to confirm the diagnostic efficacy of the LGI score in AP.Furthermore, it is worth mentioning that our results have only suggested that the LGI score can differentiate MAP in the early stage, but it does not provide further distinction between MSAP and SAP, as MSAP and SAP were combined into one group in our study.However, it is important to acknowledge that this is a challenging aspect of the current research as there has been no quick and easy way to distinguish MAP and MSAP.Fourth, several scoring systems have been well established to predict the severity of SAP, such as the Ranson score. 34Several studies 35,36 have shown that it has a AUROC of 0.81-0.83 in predicting SAP, which is significantly higher than that of the LGI score.The strength of the LGI score, compared with other scoring systems, is that it consists of only four items that are easy to be obtained at the early stage of the disease.
In conclusion, we found in this study that an increased LGI score could independently predict SAP of HTG-AP.The LGI score is easy to be obtained and therefore, can be used to assess the severity of HTG-AP.It enables a quick evaluation of the severity of AP, allowing for a prompt identification of severe cases.

2 |
PATIENTS AND METHODS 2.1 | Patients Medical records of inpatients who were diagnosed as HTG-AP at the Department of Gastroenterology, Fujian Provincial Hospital, Shengli Clinical Medical College of Fujian Medical University (Fuzhou, Fujian Province, China) from April 2012 to March 2021 were reviewed.This study was approved by the Ethics Committee of Fujian Provincial Hospital (no.K2021-02-007).The inclusion criteria of the patients were as follows: (a) patients aged 18 years or elder with confirmed diagnosis of HTG-AP; (b) hospital admission within 72 h of disease onset; and (c) CRP level, WBC and PLT counts, and NLR had been measured within 24 h after patient admission.For those experienced multiple episodes of AP, only data of the first disease episode was used for analysis.The exclusion criteria were: (a) AP of other etiologies, such as gallstones, alcohol abuse, autoimmune factors, drugs, hypercalcemia, hyperparathyroidism, and pancreatic tumors, etc; (b) patients had been treated for HTG-AP in other hospitals; and (c) those with insufficient data for analysis, in particular CRP, NLR, WBC and PLT.
Statistical analyses were performed using SPSS 25.0 (IBM, Armonk, NY, USA) and GraphPad Prism version 7.0 (GraphPad Software, San Diego, CA, USA).Normal distribution of variables was tested by the Shapiro-Wilk test when the number of cases was under 50 and by Kolmogorov-Smirnov test when the number of cases was greater than 50.Continuous variables with normal distribution were presented as mean ± standard deviation and analyzed using Student's t-test or analysis of variance (ANOVA).While those with non-normal distribution were expressed as median and interquartile range (IQR) and were analyzed using the Mann-Whitney U-test or Kruskal-Wallis test.Categorical variables were presented as numbers and proportions and analyzed using the chi-square test or Fisher's exact test.Univariate and multivariate logistic regression analyses were performed to identify independent risk factors, and odds ratio (OR) and 95% confidence interval (CI) were calculated.The discrimination of LGI score and the individual component of the score was assessed using the receiver operating characteristic (ROC) curve and the area under the ROC curve (AUROC).A P value of less than 0.05 was considered statistically significant.
Flowchart of patient enrollment and grouping.The severe acute pancreatitis group (SAP) included both moderately severe acute pancreatitis and SAP.Q1 to Q4 represented a low-grade inflammation score of ≤À5, À4 to À1, 0-4, and >4, respectively.AP, acute pancreatitis; CRP, C-reactive protein; HTG-AP, hypertriglyceridemic acute pancreatitis; MAP, mild acute pancreatitis; NLR, neutrophil-to-lymphocyte ratio; PLT, platelet; WBC, white blood cell.T A B L E 1 Baseline characteristics of the patients according to the quartiles of the low-grade inflammation (LGI) score.
Comparison of baseline characteristics of the mild acute pancreatitis (MAP) and severe acute pancreatitis (SAP) groups.
Therefore,T A B L E 2 had shown that elevated CRP, WBC, and NLR were associated with SAP, which are consistent with our results.Therefore, it can be suggested that LGI, consisting of CRP, PLT, WBC, and NLR, has a strong predictive ability for SAP.Hence, it can be inferred that LGI score plays a noteworthy role in the development of MSAP and SAP.Factors associated with the severe acute pancreatitis (SAP) group according to multivariate logistic regression analysis.