Acute pancreatitis (AP) is highly variable in terms of its clinical presentation and severity [1,2]. Many scoring systems have been developed for the early detection of severe AP, but they are not convenient for predicting the severity of AP since they involve many parameters [3-5].

Ranson's score is relatively accurate at classifying the severity of AP, but it is difficult to calculate the score as it requires a 48-hour, missing the potential for early treatment [6]. The acute physiology and chronic health examination (APACHE)-II is more accurate than Ranson's score [7], and is more commonly used to predict the severity of AP [7-9], although it was designed originally to predict intensive care unit survival and required the collection of many parameters, some of which might not be relevant to AP prognosis [10]. The Glasgow score also requires many clinical parameters and needs 48 hours to complete. In 1990, Balthazar et al. [11] described the utility of contrast-enhanced computed tomography (CT) for evaluating the severity of AP and developed the Balthazar computed tomography severity index (BCTSI) based on contrast-enhanced CT, but this system was based on local complications and did not reflect the systemic inflammatory response. The biochemical marker serum procalcitonin (PCT) is a relatively accurate and convenient method for predicting the severity in AP and is easily measured [12,13]. Some studies revealed a strong relationship between an increased serum PCT and the severity of AP [12,14,15].

In our previous study, the serum PCT level in severe AP was significantly higher than in mild AP. The accuracy of serum PCT as biochemical marker was 77.3%, which was similar to the APACHE-II score, worse than Ranson's score (93.2%), and better than the BCTSI (65.9%) [16]. In 2008, Wu et al. [17] proposed new prognostic scoring system for the early determination of the severity of AP, which they named the bedside index of severity in acute pancreatitis (BISAP). BISAP incorporates f ive parameters: blood urea nitrogen > 25 mg/dL, impaired mental status, systemic inflammatory response syndrome (SIRS), age > 60 years, and detection of pleural effusion by imaging [17,18]. SIRS is defined by the presence of at least two of the following: pulse > 90 beats per minute, respirations > 20 per minute, PaCO₂ < 32 mmHg, temperature > 38℃ or < 37℃, and white blood cell count > 12,000 or < 4,000 cells/mm³, or > 10% immature neutrophils (bands) [19,20]. A prospective validation of the BISAP scoring system as a method for the early detection of severe AP was published recently, and concluded that it is a reliable, accurate means for stratifying patients with AP [17] and that it was an accurate and convenient method of risk stratification compared with other multifactorial scoring systems in patients with AP [21]. However, the BISAP data are limited and insufficient for clinical application. The serum PCT is a simple, convenient method for predicting the severity of AP [12,14,15], with similar accuracy to the APACHE-II score [16]. As no study has compared BISAP with the serum PCT, we compared the accuracies of the BISAP, serum PCT, and other scoring systems in terms of predicting the severity of AP.

Fifty patients were enrolled in the study: 34 males and 16 females. The median patient age was 59.5 years. According to the Atlanta criteria, 26 patients were classified as mild AP and 24 as severe AP. There were no significant differences according to age (p = 0.228) and sex (p = 0.85). The causes of AP were alcoholic, biliary stone, and idiopathic or miscellaneous; differences were not significant (p = 0.465) (Table 1). Seven patients died: four of multiple organ failure and two of severe necrotizing pancreatitis; all six had severe AP, while one patient with mild AP and underlying thyroid cancer had a sudden cardiac arrest with no previous cardiac problems. The parameters according to the Atlanta criteria are described in Table 1. All six parameters were analyzed using the area under the receiver-operating curve (AUC) to predicting severe AP and the BISAP results were excellent (AUC = 0.873; p = 0.001) and the serum PCT was good (AUC = 0.788; p = 0.001) (Fig. 1). According to the analysis, Ranson's scores were the most accurate (AUC = 0.947) and the BISAP and APACHE-II scores had similar accuracy for predicting severe AP (AUC = 0.873 and AUC = 0.857, respectively). The serum PCT had relatively low accuracy (AUC = 0.788), but was better than the BCTSI score (AUC = 0.676). All six parameters were significant in terms of predicting the severity of AP (p < 0.05) (Table 2). To assess significance, BISAP scores were analyzed using two cutoff values and serum PCT levels were analyzed using four cutoff values. For the BISAP, scores of 2 were more accurate than scores of 3. For the serum PCT, 1.77 and 3.29 ng/mL had the same accuracy, but the sensitivity, positive predictive value, and likelihood ratio were higher for 3.29 ng/mL, making it the best cutoff (Table 3). The sensitivity, specificity, positive and negative predictive values, accuracy, and likelihood ratio for the other parameters with the best cutoff value were also analyzed (Table 4). Logistic regression analysis of risk factors for severe AP revealed that the odds ratios of the BISAP and serum PCT were 29.13 (≥ 2, p < 0.001) and 11.00 (≥ 3.29 ng/mL, p < 0.001), respectively (Table 5). In a simple linear regression analysis of admission duration, the BISAP had no significant relationship with hospital stay (p = 0.073), while the serum PCT was correlated with the length of hospital stay (p = 0.014), although it had a low r² value (r² = 0.118) (Fig. 2).

AP is a common disorder that places a substantial burden on the healthcare system [24]. The clinical course of AP is usually mild and it often resolves without sequelae. Nonetheless, 10% to 20% of patients experience a severe AP attack, resulting in an intense inflammatory response, a variety of local and systemic complications, a prolonged hospital course, and significant morbidity and mortality [25]. The scoring of patients with AP is important for several reasons. First, the clinician can be alerted to the presence of potentially severe disease. Second, severity can be compared both within and between patient series. Third, a rational selection of patients can be made for inclusion in trials of potential new treatments or interventions. Unfortunately, the scoring systems used at present are often inadequate in patients with severe AP, which is characterized by rapidly progressive multiple system organ dysfunction [26-28]. Therefore, a simple scoring system or single biomarker that predicts the severity of AP is needed. Serum C-reactive protein (CRP) was reported (CRP ≥ 15 mg/dL on admission) to predict severe AP with an overall accuracy of 69% [29]. Consequently, many studies have described its clinical limitation; i.e., a potential failure to detect severe cases of AP in the early stage [30-33]. Serum PCT was introduced as prognostic marker of AP, focusing on systemic inflammation and organ failure in the early stage of AP [34]. In 2008, Gurda-Duda et al. [12] stated that the early prediction of severe AP was achievable by measuring PCT, and many subsequent studies reported the efficacy of PCT as a predictor of AP, although there is some debate [14,15,30,35]. Our study revealed that the serum PCT was a significant predictor of severe AP (p = 0.018) and was consistent with our previous report [16]. In 2008, Wu et al. [17] introduced the BISAP and their results were relatively satisfactory [18,21], although more data were needed to determine its clinical applicability. In this study, we compared the BISAP with the serum PCT as a predictor of AP, and included other multifactorial scoring systems that predict the severity of AP as control parameters. In our series, Ranson's scores had the greatest accuracy for predicting the severity of AP (94%), followed by the BISAP (84%); the AUC of the BISAP was 0.873, which was superior to the results in Wu et al. [17] (AUC = 0.82) and Papachristou et al. [21] (AUC = 0.81). We found that the best cutoff score of BISAP was 2, while most other studies have proposed 3 to be the best cutoff score [17,18,21]. In our analysis, a BISAP score of 2 had greater accuracy, with a better likelihood ratio than a score of 3 (84% vs. 78% and 25.433 vs. 20.008, respectively). With a BISAP score of 2 in severe AP had 80% of SIRS, which was not observed with the same score of 2 in mild AP, which suggests that SIRS is an independent risk factor in the BISAP scoring system. In our study, the accuracy of serum PCT was 76% and the AUC was 0.788, which is similar to other reports [14,15,30,34-36]. In the analysis of four cutoff values of the serum PCT, 1.77 and 3.29 ng/mL had the same accuracy (76%), but 3.29 ng/mL had a slightly higher likelihood ratio (14.152 vs. 14.424), making 3.29 ng/mL the best cutoff level. Comparing BISAP with the serum PCT, the former had better sensitivity, specificity, accuracy, likelihood ratio, odds ratio (29.13 vs. 11.00) and p value (< 0.001 vs. 0.001) in the logistic regression analysis. Regarding the duration of hospitalization, the BISAP was not significantly related (p = 0.073), while the serum PCT had a significant p value (0.014), although r² was low (0.118). Nevertheless, the BISAP was superior to serum PCT in terms of predicting the severity of AP. We did not measure serial PCT levels because this study investigated the potential role of the PCT level in the early prediction (on the day of admission) of disease severity in patients with AP and compared it with the BISAP within 24 hours. However, Kylanpaa-Back et al. [14] demonstrated the influence of a delayed peak in PCT on predicting the severity of attacks, reporting greater sensitivity (92%) with the PCT strip test 24 hours after admission to hospital. Our study enrolled 50 consecutive patients with AP over a 14-month period: using the Atlanta classification, 52% (26/50) had mild pancreatitis and the other 48% (24/50) had severe AP. Most recent studies included only a few cases, which were usually classified as severe necrotizing pancreatitis. In contrast, our series contained only a few patients with severe necrotizing pancreatitis and the diagnosis of necrotizing pancreatitis was made using imaging tools and laboratory findings, not histologically. Therefore, we think that larger populations are needed to obtain more precise results.

In conclusion, the serum PCT is useful for predicting the severity of AP and has an accuracy similar to that of the APACHE-II score. The BISAP is relatively simple and had greater accuracy than other multifactorial scoring systems, except Ranson's score, making it a promising method of predicting the clinical severity of AP.

1. Bedside index of severity in acute pancreatitis (BISAP) scoring is simple and convenient method for predicting the severity of acute pancreatitis.

2. The accuracy of BISAP (≥ 2) at predicting severe acute pancreatitis was superior to the serum procalcitonin (≥ 3.29 ng/mL, 76%) which was similar to the acute physiology and chronic health examination (APACHE)-II score.