Efficacy of the fibrosis index for predicting end‐stage renal disease in patients with antineutrophil cytoplasmic antibody‐associated vasculitis

Objective Kidney involvement is a major manifestation of antineutrophil cytoplasmic antibody‐associated vasculitis (AAV) and may progress to end‐stage renal disease (ESRD), requiring renal replacement therapy. Unfortunately, there is no reliable kidney‐specific index for predicting the progression of renal disease to ESRD. The fibrosis index (FI) reflects the degree of fibrosis in chronic liver disease. This study aimed to investigate whether the FI at the time of diagnosis could predict the development of ESRD in AAV patients. Methods We retrospectively reviewed the medical records of 211 immunosuppressive drug‐naïve AAV patients and extrapolated the cut‐off FI value for predicting the development of ESRD using receiver operating characteristic curves. The associations between the FI and clinical outcomes, including mortality, relapse, and ESRD development, were determined. Results Overall, 39 (18.5%) patients developed ESRD owing to the progression of AAV‐associated renal disease. The median FI was higher in AAV patients with ESRD than in those without (1.61 vs 1.04; P = .001). The FI cut‐off was 1.72. The incidence of ESRD was higher in patients with FI ≥ 1.72 at the time of diagnosis than in those with an FI