Predictive value of neutrophil-to-lymphocyte ratio and fibrinogen degradation products for renal involvement in pediatric immunoglobulin A vasculitis.

Background: Immunoglobulin A vasculitis nephritis (IgAVN) is the most severe complication of IgA vasculitis (IgAV) in children, yet early predictors of renal involvement remain limited. The aim of this study is to analyse the risk factors for the development of IgAVN in children with IgAV, with a view to improving early diagnosis and treatment, reducing complications and enhancing patient prognosis. Methods: This was a retrospective analysis. A total of 100 pediatric patients with IgAV hospitalized at Children's Hospital of Fudan University Xiamen Branch (Xiamen Children's Hospital) between January 2023 and June 2025 were included in the study. Patients were divided into two groups based on the presence or absence of IgAVN. Clinical characteristics and laboratory parameters were collected. Risk factors were identified using univariate and multivariate analyses, and a risk prediction model was established using logistic regression. Model performance was evaluated using the area under the receiver operating characteristic (ROC) curve (AUC). Results: A total of 100 children with IgAV were ultimately included in this study, comprising 56 males and 44 females. They were divided into an IgAVN group (n=32) and a non-IgAVN group (n=68). Univariate analysis revealed that three laboratory parameters [C‑reactive protein (CRP), neutrophil‑to‑lymphocyte ratio (NLR), fibrinogen degradation products (FDP)] showed statistically significant differences between the IgAVN and non-IgAVN groups (P<0.05). We included the three laboratory parameters (CRP, NLR, and FDP) that showed statistically significant differences in the univariate analysis into the multivariate analysis and found that elevated NLR [odds ratio: odds ratio (OR) =1.446, 95% confidence interval (CI): 1.080-1.934, P=0.01] and elevated FDP (OR =1.854, 95% CI: 1.133-3.034, P=0.01) were independent risk factors for the development of IgAVN in children with IgAV. ROC curve analysis results showed that the AUCs for NLR >5.23 and FDP >12.35 µg/mL were 0.634 and 0.830, respectively, while the AUC for the combined NLR and FDP model was 0.882. Compared with individual indicators, the combined model demonstrated superior predictive value for IgAVN, with a sensitivity of 86.95% and a specificity of 87.40%. Conclusions: Elevated NLR and FDP are independent risk factors for the development of IgAVN in patients with IgAV. The combination of NLR >5.23 and FDP >12.35 µg/mL demonstrates good clinical predictive value for IgAVN and warrants attention from clinicians.