Prognostic value of the albumin-to-fibrinogen ratio (AFR) in IgA nephropathy patients

The albumin-to-fibrinogen ratio (AFR), a novel inflammatory marker, has been studied in various diseases. However, whether AFR could act as a prognostic factor for IgAN patients remains unclear. We aimed to investigate the prognostic value of AFR in IgAN.A total of 1289 biopsy-confirmed primary IgAN patients from 2008 to 2018 in West China Hospital, Sichuan University, were studied retrospectively. Receiver operating characteristic curve analysis was generated to assess and compare the ability of indicators to predict survival. Based on the cut-off value of AFR, IgAN patients were classified into the low AFR group and the high AFR group. The demographic and clinical-histopathological data were collected. Renal endpoints included eGFR decreased ≥50 % of the baseline level, ESRD, renal transplantation and/or death. Patients were followed up until a composite endpoint. Kaplan-Meier survival curves and Cox proportional hazards models were used to determine independent predictors.The area under the curve (AUC) of AFR was 0.677, with an optimal cut-off value of 12.44. IgAN patients were classified into two groups (low AFR group: AFR < 12.44, n = 541; high AFR group: AFR ≥ 12.44, n = 748) with a median follow-up of 55.3 (36.4-78.6) months. A higher composition of hypertension, worse renal function, higher proteinuria, and more severe pathological lesions were significantly shown in the low AFR group. Further multivariable Cox regression analyses showed that a low AFR was an independent risk factor for renal survival (HR 1.90, 95 % CI 1.29-2.81, p = 0.001). Kaplan-Meier curves showed that the cumulative incidences of both ESRD and composite end point were significantly higher in patients with AFR < 12.44 (both p < 0.001).Our study demonstrated that a low AFR (<12.44) is an independent prognostic factor of poor renal prognosis in Chinese IgAN patients.