Limited Predictive Performance of Systemic Inflammatory Indices in Acute Pancreatitis Severity

Background/Objectives: Acute pancreatitis (AP) is a heterogeneous disease with outcomes ranging from mild to severe. Early risk stratification is essential, but commonly used scoring systems are often complex for routine use. This study aimed to evaluate the predictive value of systemic inflammatory indices derived from complete blood count parameters in assessing disease severity in AP. Methods: This retrospective study included 454 patients with AP. Demographic, clinical, and laboratory data were obtained from electronic medical records. Systemic inflammatory indices (NLR, PLR, MLR, dNLR, SII, SIRI, and AISI) were calculated from admission laboratory values, with logarithmic transformation applied to selected indices. Disease severity was classified according to the Revised Atlanta Classification, and patients were grouped as mild or moderate-to-severe. Statistical analyses included ROC curve analysis and logistic regression. Results: Among 454 patients, 371 (81.7%) had mild and 83 (18.3%) had moderate-to-severe AP. Patients with more severe disease were older and showed significant differences in several laboratory parameters. NLR, PLR, SII, dNLR, and Log-SII were significantly higher in the moderate-to-severe group. However, all indices demonstrated limited discriminative performance, with dNLR showing the highest AUC (0.612). In multivariate analysis, only age and C-reactive protein (CRP) remained independent predictors of disease severity. Conclusions: Systemic inflammatory indices are associated with disease severity in AP; however, their predictive performance is limited. Conventional parameters such as age and CRP remain more reliable for risk stratification.