Discussion
We observed that early clinical characteristics have significant discriminatory value for IPN in a multicentre cohort. The prediction model, based on early clinical characteristics (temperature, RR, Ca, BUN and Glu) demonstrated robust performance in the derivation (AUC 0.85, 95% CI 0.81 to 0.89), internal cross-validation (mean AUC 0.84), and validation sets (AUC 0.82, 95% CI 0. 77 to 0.87). For high-risk patients identified by our model, subsequent monitoring and vigilance for the occurrence of IPN are recommended. In addition, our model serves as evidence supporting the initiation of antibiotic therapy, if there is the presence of sepsis or clinical deterioration, and IPN is highly suspected.10
In our model, the risk of IPN can be defined. Using a model score of 0.068 at the optimal AUC as the cut-off value, the IPN probability threshold was 0.51. The sensitivity and specificity of the model were 0.75 and 0.85, respectively. Increasing the probability threshold to 0.60 reduces sensitivity but increases specificity (to 0.23 and 0.99, respectively), thus lowering the risk of overtreatment while raising the risk of missed diagnoses. Conversely, if higher sensitivity is desired, the model threshold can be lowered. For instance, when the cut-off model score was 0.03, the sensitivity reached 0.84, but the specificity dropped to 0.67, increasing the risk of overtreatment. Therefore, a threshold that maximises the classification accuracy can be determined based on acceptable levels of false positives and false negatives. Thus, the model allows flexible selection of thresholds to define risk groups.
In the decision curve analysis, the introduction of the model significantly increased net benefits, reduced the probability of unnecessary interventions, saved healthcare resources and reduced medical costs. Given that IPN without appropriate treatment significantly increases the mortality rate of AP, the prevention of SAP and IPN is important. Currently, Vege et al24 and Ke et al25 have actively explored this field using pentoxifylline and early immune-enhancing thymosin α1, respectively. As the results were not satisfactory, further research is required. Therefore, if preventive measures for IPN are confirmed in the future, identifying high-risk patients using a model might enable early preventive treatment.
In our model, we included the first measurements taken within 24 hours of admission for RR, temperature, BUN, Ca and Glu levels. Both RR and temperature are considered evaluation indicators for SIRS reflecting the level of inflammation in the body.26 A study by Talukdar et al27 also indicated that an increase in BUN within 48 hours of admission in patients with AP can serve as a predictive indicator for IPN, consistent with our research findings. It has been believed that decreased blood calcium levels are associated with the severity of AP, which explains the rationale for incorporating this indicator in our study.28 Czapári et al suggested that glucose level at the time of admission is an independent risk factor associated with postdischarge mortality.29 Additionally, other studies have indicated that patients with on-admission hyperglycaemia are more likely to require antibiotic treatment during hospitalisation, and are associated with a higher incidence of acute necrotic collection and major infection.30 31 These findings explain why glucose level was included as an independent risk factor for IPN in our final model.
Currently, few studies are available on the early identification of IPN.13 32–35 However, these studies have relatively small sample sizes and some lack validation, which limits the reliability and generalisability of their findings. Despite providing instructive results, the predictive efficacy of these models may not always be satisfactory. Chen et al33 and Wiese et al34 focused specifically on necrotising pancreatitis, with their models exhibiting good performance, with AUCs of 0.79 and 0.82, respectively. However, it is important to note that the impairment of pancreatic perfusion and signs of peripancreatic necrosis evolved over several days.9 Therefore, the use of these models requires that there be no missed diagnoses of necrotising pancreatitis. In contrast, our model can be applied to all adult patients with AP, offering greater convenience, and has shown superior performance in both the training and validation data sets. Similarly, Song et al35 focused on a specific group of patients with AP (moderately severe and severe AP). Zhu et al36 proposed an IPN prediction model based on a modified CT Severity Index, neutrophil-to-lymphocyte ratio and procalcitonin on the seventh day postadmission. In terms of predictive performance, their model demonstrated a high AUC of 0.92 on the training data set. Despite robust performance, their model has not been validated, presenting a risk of overfitting. Furthermore, our study included indicators that might be obtained on the day of admission, enabling more rapid and convenient IPN prediction. Mao et al13 demonstrated the effectiveness of mPASS-4 for predicting IPN in a prospective clinical trial including 508 cases of acute necrotising pancreatitis, achieving an AUC of 0.75. This research underscored the potential of PASS for predicting IPN.37 However, due to the lack of certain data types in our cohort, we were unable to compare PASS, mPASS-4 and our model. Future research should focus on comparative studies of these existing models using larger sample sizes. Apart from predicting IPN, Trikudanathan et al38 developed a model to predict the need for intervention in acute necrotising pancreatitis after discharge, with an AUC of 0.88. This model provides a valuable tool for managing patients with IPN from different perspectives.
However, our study has limitations. It was retrospective, which may have introduced selection bias, as the inpatients may have severe disease, resulting in a higher incidence of IPN. Additionally, the incidence of hypertriglyceridemic pancreatitis in China is higher than that in Europe and USA, as observed in our cohort.39 40 Therefore, when applying the model to regions such as Europe and USA, it is important to consider population-specific factors and conduct additional external validation beyond China. Furthermore, in our multicentre study, we did not include other inflammatory markers, such as interleukin-6, or additional peripheral blood information, including proteomics, radiomics and other potential factors. This may have reduced the predictive accuracy of our model. This area will be further explored in the future to enhance the accuracy of predictive models.