Prognostic nutritional index as an independent risk factor for disease progression in patients with IgA nephropathy

Immunoglobulin A nephropathy (IgAN), a common primary glomerulonephritis worldwide, has been investigated, and complex factors are involved in disease progression. A group of evidence emerged that nutrition status plays a nonsubstitutable role in the management of chronic kidney disease. Meanwhile, a novel marker of nutrition and inflammation, the prognostic nutritional index (PNI), has been studied in various diseases. Whether PNI can predict the renal outcome of patients with IgAN remains unclear. Thus, we aimed to evaluate the relationships between PNI and clinicopathologic features, renal progression and renal prognosis in patients with IgAN.

A total of 1,377 patients with biopsy-proven IgAN were recruited for this retrospective study. All patients were divided into two groups based on the cutoff value of PNI: the high group (PNI ≥ 47.1, n = 886) and the low group (PNI < 47.1, n = 491). Our study endpoint was end-stage renal disease [estimated glomerular filtration rate (eGFR) < 15 mL/min/1.73 m² or performance of renal replacement therapy]. A correlation test was conducted to explore the relationship between PNI and other important clinicopathologic parameters. The predictive value was determined by the area under the receiver operating characteristic curve (AUROC). Kaplan-Meier and Cox proportional hazards analyses were performed to assess the value of PNI in predicting renal progression and prognosis.

The correlation test revealed that PNI was positively associated with eGFR (r = 0.16, p < 0.001) and negatively related to 24-h proteinuria (r = -0.387, p < 0.001). Multivariate Cox regression analysis indicated that low PNI was an independent risk factor for IgAN patients even after adjusting for important clinical and pathological parameters (HR, 0.664; 95% CI, 0.443-0.994; p = 0.047). Kaplan-Meier analysis showed that low PNI was significantly correlated with severe renal outcome in patients with IgAN (p < 0.001). Moreover, the subgroup analyses of Kaplan-Meier survival demonstrated that low PNI predicted severe renal prognosis in different types of IgAN patients when considering the level of glomerular filtration rate, 24 h proteinuria and hemoglobin.

PNI is associated with renal function and pathologic lesions in IgAN patients and could be a novel marker for the evaluation of renal progression and prognosis.