Combined Fibrinogen and Urinary α1-Microglobulin as Predictors of Respiratory Tract Infection in Children with Nephrotic Syndrome.

BACKGROUND Respiratory tract infections (RTIs) are a major complication and prognostic determinant in children with nephrotic syndrome (NS), yet reliable predictors for infection risk remain lacking. Although fibrinogen (FIB) and urinary a1-microglobulin (alpha1-MG) have been individually linked to inflammation and renal injury, their combined prognostic value in pediatric NS has not been established. This study investigated the correlation between FIB, urinary alpha1-MG, and RTI occurrence in children with NS and evaluated whether their combined measurement improves early RTI risk prediction and prognosis assessment. MATERIAL AND METHODS Eighty children with NS and 70 age-matched healthy controls were enrolled. Serum FIB and urinary alpha1-MG levels were compared between groups. NS patients were stratified retrospectively into a good-prognosis group (n=50; no RTI during follow-up) and a poor-prognosis group (n=30; RTI occurrence), based on clinical outcomes rather than randomization. Clinical characteristics were assessed, and multivariate logistic regression identified independent risk factors for RTI. Correlation analysis and combined biomarker predictive modeling were performed. RESULTS FIB and urinary a1-MG levels were significantly elevated in NS patients compared to controls. RTI risk was independently associated with younger age, longer hospital stay, lower albumin, and lack of vitamin A/D supplementation. Both FIB and urinary alpha1-MG were positively correlated with RTI occurrence, with higher levels in the poor-prognosis group (P<0.05). The combination of FIB and urinary alpha1-MG demonstrated superior predictive accuracy for RTI compared with either marker alone (AUC >0.917). CONCLUSIONS This study is the first to identify the combined measurement of FIB and urinary a1-MG as a possible independent predictor of RTI in children with NS. These findings provide a promising biomarker-based approach for early risk assessment, enabling targeted interventions to reduce RTI occurrence, shorten hospitalization, and ultimately improve prognosis in pediatric NS.