Nonalbumin Protein-to-Creatinine Ratio in IgA Nephropathy: Clinical and Pathological Correlations

Background: Although albuminuria is beneficial for the early detection of kidney disease, it is insufficient for the characterization of tubular and hyperfiltration proteinuria. This study evaluated the non-albumin protein-to-creatinine ratio (NAPCR) in patients with IgA nephropathy, from both clinical and pathological perspectives. Methods: This study included 59 patients diagnosed with IgA nephropathy via kidney biopsy at our hospital between June 2022 and November 2023. NAPCR (g/gCr) was determined by subtracting urinary albumin (ACR) from urinary protein (PCR). The clinical grade (C-grade) of IgA nephropathy at the time of biopsy was assessed according to the criteria of the Japanese Society of Nephrology (JSN) criteria. Histological severity was classified based on the JSN histological grading criteria or the Oxford classification. Risk stratification for dialysis was determined by combining clinical and histological grades (H-grade) according to the JSN and categorized into low, medium, high, or super-high risk of progression to end-stage kidney disease (ESKD). Results: he average age of the patients was 48 years (31 males, 53.4%). The mean estimated glomerular filtration rate (eGFR) was 56.3 ml/min/1.73m<span style="font-size:10.8333px">2</span>. The average PCR was 0.51 g/gCr, and the ACR was 0.35 g/gCr. Higher NAPCR values correlated with increased clinical and histological severity (Table), whereas PCR did not correlate with histological severity. Conclusion: NAPCR was significantly associated with clinical and histological severity of IgA nephropathy.