Abstract
BackgroundProteinuria is a target for renoprotection in kidney diseases. However, optimal level of proteinuria reduction in IgA nephropathy (IgAN) is unknown.MethodsWe conducted a retrospective observational study in 500 patients with biopsy-proven IgAN. Time-averaged proteinuria (TA-P) was calculated as the mean of every 6 month period of measurements of spot urine protein-to-creatinine ratio. The study endpoints were a 50% decline in estimated glomerular filtration rate (eGFR), onset of end-stage renal disease (ESRD), and slope of eGFR.ResultsDuring a median follow-up duration of 65 (12–154) months, a 50% decline in eGFR occurred in 1 (0.8%) patient with TA-P of <0.3 g/g compared to 6 (2.7%) patients with TA-P of 0.3–0.99 g/g (hazard ratio, 2.82; P = 0.35). Risk of reaching a 50% decline in eGFR markedly increased in patients with TA-P of 1.0–2.99 g/g (P = 0.002) and those with TA-P≥3.0 g/g (P<0.001). ESRD did not occur in patients with TA-P<1.0 g/g compared to 26 (20.0%) and 8 (57.1%) patients with TA-P of 1.0–2.99 and ≥3.0 g/g, respectively. Kidney function of these two groups deteriorated faster than those with TA-P<1.0 g/g (P<0.001). However, patients with TA-P of 0.3–0.99 g/g had a greater decline of eGFR than patients with TA-P<0.3 g/g (−0.41±1.68 vs. −0.73±2.82 ml/min/1.73 m2/year, P = 0.03).ConclusionIn this study, patients with TA-P<1.0 g/g show favorable outcomes. However, given the faster eGFR decline in patients with TA-P of 0.3–0.99 g/g than in patients with TA-P<0.3 g/g, the ultimate optimal goal of proteinuria reduction can be lowered in the management of IgAN.
Highlights
IgA nephropathy (IgAN) is slowly progressive and 20–30% of patients with IgAN will require renal replacement therapy within 20–25 years after disease onset [1,2]
TA-blood pressure (BP), serum concentrations of total cholesterol and triglycerides, 24-h urine protein excretion, urine urine proteincreatinine ratio (UPCR), MEST score, and absolute renal risk (ARR) score were significantly higher in patients with higher time-averaged proteinuria (TA-P) (P for trend,0.001). estimated glomerular filtration rate (eGFR) (P for trend = 0.04) and serum albumin levels (P for trend,0.001) were lower in patients with higher TA-P
These findings suggest that proteinuria reduction to,1.0 g/day suggested by the KDIGO guideline [18] is acceptable, but the ultimate therapeutic goal of proteinuria reduction for renoprotection in IgAN can be modified
Summary
IgA nephropathy (IgAN) is slowly progressive and 20–30% of patients with IgAN will require renal replacement therapy within 20–25 years after disease onset [1,2]. The optimal target for proteinuria reduction to attenuate progression of kidney disease is currently unknown. A favorable outcome is more likely for patients with IgAN that have proteinuria ,1 g/ day throughout the disease course, there is controversy on whether further reduction of proteinuria below this level will provide additional benefit [11,12]. The purpose of this study was, to identify the optimal target for proteinuria reduction for renoprotection in patients with IgAN. To this end, we used time-averaged proteinuria (TA-P) and classified patients into four groups according to TA-P levels. We aimed to investigate whether reducing proteinuria below the level that the current guideline suggests may improve renal outcome. Optimal level of proteinuria reduction in IgA nephropathy (IgAN) is unknown
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