Prognostic nutritional index is associated with clinical and histopathological severity in IgA nephropathy

Objective The prognostic nutritional index (PNI) reflects immunonutritional status and serves as a prognostic marker in various diseases. However, its clinical significance in IgA nephropathy (IgAN) remains poorly understood. We investigated the association between PNI and clinico-pathological severity as well as long-term kidney outcomes in IgAN.Methods We retrospectively analyzed 153 patients with biopsy-proven IgAN. Patients were categorized into four PNI groups (<40, 40–50 [reference], 50–55, and ≥55). The primary outcome was urine protein-to-creatinine ratio (UPCR) at biopsy; secondary outcomes were pathological severity (Oxford MEST-C and Haas classifications) and a composite kidney outcome (creatinine doubling, ≥40% eGFR decline, or dialysis initiation).Results In the fully adjusted models, the lowest PNI group (<40) exhibited a 3.49-fold higher UPCR (AMR 3.49; p < 0.001) and was independently associated with segmental sclerosis (S1) (OR 5.09; p=0.029) and crescents (C1/2) (OR 3.81; p=0.031). Conversely, the highest PNI group (≥55) showed lower UPCR (AMR 0.47; p<0.001), reduced risk of advanced tubular atrophy/interstitial fibrosis (T1/2) (OR 0.31; p=0.042), and lower Haas stages (OR 0.29; p=0.010). Although the association with long-term outcomes was attenuated after UPCR adjustment in the total cohort, the lowest PNI group maintained a highly significant risk among patients with non-nephrotic range proteinuria (HR 17.99; p=0.006).Conclusion PNI was associated with proteinuria and histological severity in IgAN and may provide additional prognostic information for long-term kidney outcomes beyond proteinuria alone, particularly in patients with non-nephrotic-range proteinuria.