Supplementary file 1_Association of the inflammation indicators with multiple system involved of immunoglobulin A vasculitis in children.docx

Generalized additive models (GAM) and ROC curve analysis were used to determine optimal cut-off values for age and disease duration.</p>Results<p>Multi-system involvement was the most common phenotype (45.2%). Compared with other subgroups, multi-system involvement patients showed significantly higher WBC (P = 0.032), neutrophils (P = 0.001), platelets (P = 0.002), NLR (P = 0.001), PLR (P = 0.002), and D-dimer, while albumin was lowest (P < 0.001).

Pairwise comparisons revealed that NLR and PLR elevations were most pronounced between multi-system and skin-only groups. GAM analysis identified 10 years as the optimal cut-off for onset age; children >10 years had significantly higher renal involvement rates (25.49% vs. 11.39%, P < 0.001) and higher NLR (P = 0.019) than those ≤10 years. Multivariate logistic regression identified female sex (OR = 1.650, P = 0.038), onset age >10 years (OR = 2.160, P = 0.036), and longer disease duration (OR = 1.059, P = 0.037) as independent risk factors for renal involvement.</p>Conclusion<p>Elevated inflammatory markers including WBC, neutrophils, platelets, NLR, PLR, and D-dimer, as well as decreased albumin, are associated with multi-system involvement in children with IgAV, with the most pronounced differences observed between multi-system and skin-only groups.

Onset age >10 years is associated with increased renal involvement risk. These routine laboratory indicators, interpreted in conjunction with age and disease duration, may aid in early risk stratification.</p>