Clinical significance of urinary inflammatory biomarkers in patients with IgA nephropathy

Background: IgA nephropathy (IgAN) is the most common type of primary glomerulonephritis, although the definitive markers are unknown. We aimed to investigate the clinical significance of urinary cytokines in patients with IgAN. Methods: From 2009 to 2018, the patients were divided into three groups: IgAN (n = 191), disease control (n = 53), and normal control (n = 76). We used a multiplex enzyme-linked immunosorbent assay to measure 16 selected urinary inflammatory cytokines, evaluated the correlation between clinical and pathological features following regression analysis on progression. Results: The IgAN group exhibited significantly different levels of urinary cytokines compared to the normal control and disease control groups. Urinary levels of B-cell-activating factor, vascular endothelial growth factor receptor-2, monocyte chemoattractant protein-1, C–X–C motif chemokine 10, C–X–C motif ligand 16, epidermal growth factor (EGF), endocan, endostatin, growth/differentiation factor-15 (GDF-15), interleukin-6 (IL-6), mannose-binding lectin, transferrin receptor, and kidney injury molecule-1 were significantly correlated with both the estimated glomerular filtration rate and urine protein–creatinine ratio. In a multivariate Cox regression analysis, urinary EGF (hazard ratio [HR] 0.40, 95% confidence interval [CI] 0.17–0.95, P = 0.04), GDF-15 (HR 2.45, 95% CI 1.01–5.94, P = 0.048), and IL-6 (HR 3.02, 95% CI 1.05–8.64, P = 0.04) were associated with progression in IgAN. Conclusions: Urinary inflammatory biomarkers may serve as alternative predictive biomarkers in patients with IgAN. Further studies are needed to elucidate the physiological mechanisms and confirm the results.