FGF23, Albuminuria, and Disease Progression in Patients with Chronic IgA Nephropathy

BackgroundOn the basis of findings of observational studies and a meta-analysis, proteinuria reduction has been proposed as a surrogate outcome in IgA nephropathy. How long a reduction in proteinuria needs to be maintained to mitigate the long-term risk of disease progression is unknown.MethodsIn this retrospective multiethnic cohort of adult patients with IgA nephropathy, we defined proteinuria remission as a ≥25% reduction in proteinuria from the peak value after biopsy, and an absolute reduction in proteinuria to <1 g/d. The exposure of interest was the total duration of first remission, treated as a time-varying covariate using longitudinal proteinuria measurements. We used time-dependent Cox proportional hazards regression models to quantify the association between the duration of remission and the primary outcome (ESKD or a 50% reduction in eGFR).ResultsDuring a median follow-up of 3.9 years, 274 of 1864 patients (14.7%) experienced the primary outcome. The relationship between duration of proteinuria remission and outcome was nonlinear. Each 3 months in sustained remission up to approximately 4 years was associated with an additional 9% reduction in the risk of disease progression (hazard ratio [HR], 0.91; 95% confidence interval [95% CI], 0.89 to 0.93). Thereafter, each additional 3 months in remission was associated with a smaller, nonsignificant risk reduction (HR, 0.99; 95% CI, 0.96 to 1.03). These findings were robust to multivariable adjustment and consistent across clinical and histologic subgroups.ConclusionsOur findings support the use of proteinuria as a surrogate outcome in IgA nephropathy, but additionally demonstrate the value of quantifying the duration of proteinuria remission when estimating the risk of hard clinical endpoints.

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

Frontiers in Medicine ◽

10.3389/fmed.2021.792782 ◽

2021 ◽

Vol 8 ◽

Author(s):

Xiaoqi Shen ◽

Jun Cheng ◽

Guizhen Yu ◽

Xiayu Li ◽

Heng Li ◽

...

Keyword(s):

Renal Disease ◽

Disease Progression ◽

Iga Nephropathy ◽

Cubic Splines ◽

Retinol Binding Protein ◽

Renal Outcome ◽

Renal Disease Progression ◽

Renal Outcomes ◽

Β2 Microglobulin ◽

Restricted Cubic Splines

Background: Tubulointerstitial involvement has been reported to have a decisive influence on the progression of IgA nephropathy (IgAN). High levels of urine β2-microglobulin (β2-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 β2-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 β2-MG, and RBP at the time of biopsy were collected. The associations, of urine β2-MG and RBP with the composite renal outcome, defined as a decline in estimated glomerular filtration rate (eGFR) of ≥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 β2-MG and RBP levels had worse renal outcomes. The Cox regression analysis revealed that urine β2-MG and RBP were associated with a risk of the composite renal outcome in the multivariate adjusted model [+1 SD for log β2-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 m2 (+1 SD for log β2-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 ≥90 ml/min/1.73 m2.Conclusion: Higher levels of urine β2-MG and RBP were independent risk factors for renal disease progression in IgAN.

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