Abstract:Objective To investigate the predictive value of complement C3 and chitinase-3-like protein 1 (CHI3L1) in the prognosis of henoch-sch?nlein purpura nephritis (HSPN) in children, and to construct a combined predictive model and prevention strategy, thereby providing a basis for the early identification and treatment of high-risk pediatric patients.Methods A total of 100 pediatric HSPN patients were enrolled at a 1:1 ratio to Beijing Anzhen Nanchong Hospital of Capital Medical University (Nanchong Central Hospital) from January 2020 to December 2024 were retrospectively analyzed. Based on follow-up outcomes, patients were divided into a good prognosis group and a poor prognosis group (n = 50 each). Data including age of onset, laboratory parameters, and clinical features were collected. Univariate and multivariate logistic regression analyses were used to identify prognostic factors. The receiver operating characteristic (ROC) curve, precision-recall (PR) curve, and model quality score were employed to evaluate the predictive performance of individual markers and the combined model.Results No significant differences were observed between the good- and poor-prognosis groups regarding sex, age at onset, disease duration, macroscopic hematuria, abdominal or joint pain, anemia, hypoalbuminemia, RAS inhibitor or immunosuppressive therapy, and cholesterol levels (P > 0.05). The poor-prognosis group showed higher ISKDC grading, neutrophil count, WBC, RDW, D-dimer, proteinuria, NAG/UCr, CRP, CHI3L1,PLT, frequency of purpura ≥ 3 times, rash duration ≥ 2 weeks, hyperuricemia rate, and longer interval from kidney involvement to biopsy, but lower complement C3, and shorter rash-to-kidney involvement interval (P < 0.05). Multivariate logistic regression identified elevated ISKDC grading [O^R = 2.339 (95% CI: 1.248,4.385) ], neutrophil count [O^R = 2.955 (95% CI: 1.077, 4.508) ], CHI3L1 [O^R = 1.353 (95% CI: 1.109, 1.651) ], and decreased complement C3 [O^R = 0.002 (95% CI: 0.000, 0.338) ] as independent risk factors for poor prognosis (P < 0.05). ROC analysis showed AUCs of 0.706 (ISKDC), 0.813 (neutrophil), 0.728 (C3), 0.819 (CHI3L1), and 0.937 for the combined model, with sensitivities of 76.0%, 78.0%, 84.0%, 78.0%, 88.0%, and specificities of 56.0%, 76.0%, 56.0%, 84.0%, 94.0%. Internal validation confirmed good calibration (AUC = 0.906, P > 0.05).Conclusion ISKDC grade, NEU, CHI3L1, and complement C3 are potential biomarkers for predicting prognosis in HSPN children. The combined predictive model based on these indicators demonstrates strong discriminatory ability and clinical applicability, enabling effective identification of high-risk patients. Based on the model assessment results, individualized intervention strategies including early corticosteroid pulse therapy, immunomodulation, combined antifibrotic therapy, and dynamic monitoring of relevant indicators are proposed to optimize the prognostic management of HSPN children.