Urine β2-Microglobulin and Retinol-Binding Protein and Renal Disease Progression in IgA Nephropathy

Background: Tubulointerstitial involvement has been reported to have a decisive influence on the progression of IgA nephropathy (IgAN). High levels of urine beta 2-microglobulin (beta 2-MG) and retinol-binding protein (RBP) were observed in patients with IgAN with tubulointerstitial lesions. However, their roles in disease progression remain unclear. This study aimed to evaluate the associations of urine beta 2-MG and RBP with the progression of IgAN.Methods: We retrospectively investigated a cohort of 2,153 patients with IgAN. Clinical and pathological features, outcomes, and urine beta 2-MG, and RBP at the time of biopsy were collected. The associations, of urine beta 2-MG and RBP with the composite renal outcome, defined as a decline in estimated glomerular filtration rate (eGFR) of & GE;50% from baseline or end-stage renal disease (ESRD), were examined using restricted cubic splines and the Cox proportional hazards models.Results: During a median follow-up of 20.40 months, 140 (6.50%) patients reached the composite renal outcomes. Restricted cubic splines showed that patients with higher urinary beta 2-MG and RBP levels had worse renal outcomes. The Cox regression analysis revealed that urine beta 2-MG and RBP were associated with a risk of the composite renal outcome in the multivariate adjusted model [+1 SD for log beta 2-MG, hazard ratio (HR) = 1.462, 95% CI: 1.136-1.882, p = 0.003; +1 SD for log RBP, HR = 1.972, 95% CI: 1.486-2.617, p = 0.001]. The associations were detectable within patients with baseline eGFR < 90 ml/min/1.73 m(2) (+1 SD for log beta 2-MG, HR = 1.657, 95% CI: 1.260-2.180, p < 0.001; +1 SD for log RBP, HR = 1.618, 95% CI: 1.199-2.183, p = 0.002), but not among patients with eGFR & GE;90 ml/min/1.73 m(2).Conclusion: Higher levels of urine beta 2-MG and RBP were independent risk factors for renal disease progression in IgAN.

Automated summary

This study retrospectively investigated 2,153 patients with IgA nephropathy and found that higher levels of urine beta 2-microglobulin and retinol-binding protein were associated with worse renal outcomes. Urine beta 2-MG and RBP were identified as independent risk factors for renal disease progression in IgAN.