The predictive accuracy of systemic immune-inflammation index and lymphocyte-to-monocyte ratio for extrapulmonary complications in pediatric

Background: The prediction of extrapulmonary complications (EP complications) in pediatric Methods: A total of 160 pediatric MPP cases who visited Capital Center for Children's Health, Capital Medical University, between January 2025 and February 2025 were retrospectively analyzed. The patients were recruited using a consecutive sampling method, and the cases were divided into two categories depending on whether EP complications were present, forming the MPP group (n=112) and the MPP + EP group (n=48). EP complications were defined using a composite reference standard, which included skin involvement, gastrointestinal symptoms, circulatory complications, hematologic abnormalities, urinary manifestations, and arthritis. Baseline characteristics of both groups were compared to assess differences in demographic and clinical factors. To explore potential factors associated with EP complications, both univariate and multivariate logistic regression models were utilized. The ability of SIRI, LMR, and C-reactive protein (CRP) to indicate diagnostic relevance was assessed through receiver operating characteristic (ROC) curve analysis, with the area under the curve (AUC) computed for performance evaluation. Results: Cases in the MPP + EP group showed longer hospitalization, higher white blood cell (WBC) counts, and elevated CRP levels compared to the MPP group (P<0.001). SIRI was significantly higher (P<0.001), while LMR was lower (P=0.001) in cases with EP complications. Multivariate logistic regression identified SIRI [odds ratio (OR) =1.007, P<0.001], CRP (OR =1.199, P=0.03), and LMR (OR =0.143, P<0.001) as independent predictors. ROC analysis showed that SIRI had the highest predictive accuracy (AUC =0.824, sensitivity =75.0%, specificity =89.3%), followed by CRP (AUC =0.717, sensitivity =77.1%, specificity =62.5%) and LMR (AUC =0.673, sensitivity =58.9%, specificity =70.8%). The combination of SIRI, CRP, and LMR improved performance (AUC =0.858, sensitivity =75.0%, specificity =92.9%). The cross-tabulation of test results against the reference standard showed that for CRP, 42 MPP cases and 37 MPP + EP cases were positive, and 70 MPP cases and 11 MPP + EP cases were negative. For SIRI, 12 MPP cases and 36 MPP + EP cases were positive, and 100 MPP cases and 12 MPP + EP cases were negative. For LMR, 46 MPP cases and 34 MPP + EP cases were positive, and 66 MPP cases and 14 MPP + EP cases were negative. Conclusions: SIRI and LMR are valuable inflammatory biomarkers for predicting EP complications in pediatric MPP cases. Higher SIRI and CRP levels were linked to an increased risk of extrapulmonary involvement, while lower LMR appeared to be protective. The combination of these markers enhances predictive accuracy, supporting their potential clinical utility in risk stratification and early intervention strategies.