Abstract
BACKGROUND: There are currently no definitive or reliable methods for diagnosing complicated appendicitis in preschool children. This study aimed to identify the independent risk factors for complicated appendicitis to assist clinicians in assessing the severity of appendicitis in preschool children. METHODS: We conducted a retrospective analysis of 258 preschool-aged patients from January 2021 to December 2023, including 99 cases with complicated appendicitis and 159 cases with uncomplicated appendicitis. The characteristics of clinical symptoms and laboratory data were collected, and then the Pediatric Appendicitis Score (PAS) was calculated. Univariate and multivariate analyses were performed to identify the independent risk factors for complicated appendicitis. The receiver operating characteristic (ROC) curve and the area under the ROC curve (AUC) were used to assess the diagnostic performance of these indicators. RESULTS: Univariate analysis revealed significant differences in PAS, neutrophil-to-lymphocyte ratio (NLR), and C-reactive protein (CRP) levels between complicated and uncomplicated appendicitis (p < 0.05). And these three parameters were also confirmed to be independent risk factors for complicated appendicitis by further multivariate regression analysis. The PAS demonstrated a moderate diagnostic performance in distinguishing complicated appendicitis, with an optimal cut-off value of 8, sensitivity of 77.8% and specificity of 49.1% (AUC: 0.678, 95%CI: 0.614 ~ 0.743). And CRP alone seems to provide a higher AUC of 0.809(95%CI: 0.755–0.864) with the sensitivity of 79.8% and specificity of 76.1%. Additionally, the combination of these three variables yielded a further, albeit marginal, improvement in diagnostic efficacy. CONCLUSION: The PAS, NLR, and CRP are identified as independent predictors for identifying complicated appendicitis. Moreover, the combination of PAS, NLR, and CRP allows clinicians to better differentiate complicated appendicitis, thus facilitating clinical decision-making in preschool children. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12887-026-06535-w.